IS-IS

Intermediate System-to-Intermediate System (IS-IS) intra-domain routing information exchange protocol is designed by the International Organization for Standardization to support connectionless networking. This protocol is a dynamic routing protocol.

IS-IS Introduction

IS-IS is a link-state protocol, which uses the Shortest Path First (SPF) algorithm. IS-IS and the OSPF protocol are similar in many aspects. As an Interior Gateway Protocol (IGP), IS-IS runs inside an Autonomous System (AS).

To enable IS-IS, you must instantiate an IS-IS routing instance and assign it to an interface. Arista IS-IS support includes IS-IS segment routing and IS-IS graceful restart.

IS-IS Segment Routing

Segment Routing (SR) provides a mechanism to simplify the definition of end-to-end paths within IGP topologies by encoding paths as sequences of topological sub-paths, called segments. The IS-IS protocol advertises these segments in four different ways: node segments, prefix segments, proxy-node segments, and adjacency segments.

Node segments represent a node in an IGP topology. A proxy segment are generally associated with an IP(v6) address received from a router that does not support IS-IS SR. Prefix segments represent an ECMP-aware shortest path to a prefix (or a node), as per the state of the IGP topology. Adjacency segments represent a hop over a specific adjacency between two nodes in IGP.

TI-LFA FRR using IS-IS Segment-Routing

Topology Independent Fast Reroute, or TI-LFA, uses IS-IS SR to build loop-free alternate paths along the post-convergence path. These loop-free alternates provide fast convergence in the range of sub-50 ms.

This section describes TI-LFA FRR using II-IS SR, including configuration instructions and command descriptions. Topics covered by this chapter include:

The (Point of Local Repair (PLR)- the router where TI-LFA is configured) PLR switches to these loop-free alternate backup paths in the event of a link down (link-protection) or BFD neighbor down (node-protection) event, protecting traffic destined to IS-IS SR node segments, adjacency segments, and anycast segments while the IGP converges and the post-convergence paths are computed. Anycast segment protection is restricted to those segments which are attached to prefixes with host mask (/32 for V4 address and /128 for v6 address).

Note: Unlike node segments, anycast segments do not have the ‘N’ flag set described in section 2.1.1.2 of RFC8667.
The following enhancements are available by release:
  • EOS Release 4.22.1F adds support for TI-LFA backup paths that protect IS-IS SR labeled traffic corresponding to a node segment or adjacency segment on a transit router.
  • EOS Release 4.23.1F adds support for TI-LFA backup paths that protect IS-IS SR tunnels.
  • EOS Release 4.24.1 adds support for protecting IS-IS SR labeled traffic corresponding to anycast segments.
  • EOS Release 4.24.2F adds support for calculating TI-LFA backup paths that exclude the SRLG configured on the failing link.

Backup paths are only installed for IS-IS SR labeled routes and tunnels corresponding to node segments, adjacency segments, and anycast segments. When requesting node-protection, and no node-protecting LFAs are available, a link-protecting LFA is computed instead. TI-LFA FRR using IS-IS Segment-Routing is available with the multi-agent routing protocol model and the ribd routing protocol model.

Other traffic that resolves over IS-IS SR tunnels, such as LDP pseudowires, BGP LU tunnels, BGP IP routes, L2 EVPN, MPLS L3 VPN, and so on, are also protected by the TI-LFA tunnel that protects the resolving IS-IS SR tunnel.

Limitations

  • Backup paths are not computed for prefix segments that do not have a host mask (/32 for v4 and /128 for v6).
  • When TI-LFA is configured, the number of anycast segments generated by a node cannot exceed 10.
  • Computing TI-LFA backup paths for proxy node segments is not supported.
  • Backup paths are not computed for node segments corresponding to multi-homed prefixes. The multi-homing could be the result of them being anycast node segments, loopback interfaces on different routers advertising SIDs for the same prefix, node segments leaked between levels, and thus being seen as originated from multiple L1-L2 routers.
  • Backup paths are only computed for segments that are non-ECMP.
  • Only IS-IS interfaces that are using the point-to-point network type are eligible for protection.
  • Link/node protection is only supported in the default VRF owing to the lack of non-default VRF support for IS-IS segment-routing.
  • Backup paths are computed in the same IS-IS level topology as the primary path.
  • Even with IS-IS GR configured, ASU2, SSO, agent restart are not hitless events for IS-IS SR LFIB routes or tunnels being protected by backup paths.

IS-IS Graceful Restart

IS-IS Graceful Restart (GR) is a mechanism to prevent routing protocol re-convergence during a processor switchover or device downtime. Normally, when a router restarts, all the neighboring routers associated with that router detect that the device has gone down and remove routes from that neighbor. When the router restarts, the session is re-established and data transfer continues. During the restart, the removal and re-insertion of routes will result in data loss. This can be prevented by configuring graceful restart on the device.

When IS-IS is used as the interior gateway protocol (IGP), the following EOS features require nonstop forwarding (NSF) and support for the graceful restart from IS-IS:
  • Accelerated Software Upgrade phase 2 (ASU2).
  • planned Stateful SwitchOver (SSO) initiated by an operator for maintenance, or unplanned SSO due to failures on the active supervisor.
  • RIB agent restart due to software failures.

With IS-IS Graceful Restart (GR) configured, a redundancy switchover from active to standby supervisor, or ASU2, or restart of the IS-IS software (the RIB agent) should be a hitless event if the GR completes successfully. Neighboring routers will continue to forward traffic to the restarting router and traffic forwarding through the restarting router continues without loss. If GR is successful, the failure of a router should be completely transparent to network applications.

ISIS Graceful Restart (GR) is compatible with the following platforms:
  • IS-IS GR with unplanned software restart is supported on all platforms.
  • IS-IS GR with SSO is supported on modular dual-supervisor platforms.
  • IS-IS GR with ASU2 is supported on platforms that support ASU2.

IS-IS Dynamic Flooding

Dynamic Flooding allows IS-IS to scale to large, dense topologies such as Leaf-Spine topologies. In such topologies, legacy IS-IS can exhibit a congestive collapse due to the control plane load created by excessively redundant flooding.

The concept in Dynamic Flooding is to dynamically compute a restricted topology for flooding (the flooding topology). Since this can be much smaller than the full physical topology, this can reduce the redundancy seen by each node, thereby reducing the control plane load and avoiding a congestive collapse.

To do this, first select one node within the IS-IS area as the area leader. Leverage the Designated Intermediate System (DIS) election algorithm for this, except instead of applying it to the neighbors on an interface, compute it across all of the nodes within the area.

The area leader is responsible for computing the flooding topology. This is distributed to the other nodes in the area through the Area System IDs TLV and the Flooding Path TLV.

All nodes within the area then flood only on the flooding topology.

Figure 1. Flooding Topology

A flooding topology on a dense graph. The flooding topology is shown by the solid lines. Dotted lines indicate non-flooding links.

In a dense topology, this can reduce the amount of flooding by an order of magnitude or more, with a resulting increase in scalability.

IS-IS Configuration

Enabling IS-IS

Enabling IS-IS Globally and Specifying an IS-IS Instance

The switch supports only one IS-IS routing instance per VRF. The routing instance uniquely identifies the switch to other devices. IS-IS configuration commands apply globally to the IS-IS instance.

The switch must be in router IS-IS configuration mode to run IS-IS configuration commands. The router isis command places the switch in router IS-IS configuration mode.

Example

These commands create an IS-IS routing instance named Osiris in the default VRF and place the switch in IS-IS configuration mode for that instance.
switch(config)#router isis Osiris
switch(config-router-isis)#

Configuring the Network Entity Title (NET)

After creating an IS-IS routing instance, configure the Network Entity Title (NET) with the net command. The NET defines the IS-IS area address and the system ID of the device.

Example

These commands configure the NET by specifying the IS-IS area address and the system ID of the device.
switch(config)#router isis Osiris
switch(config-router-isis)#net 49.0001.1010.1040.1030.00

Setting the Address Family Configuration

The address-family command enables the address families that IS-IS will route and places the switch in the configuration mode for that address family. The address families supported are IPv4 unicast and IPv6 unicast.

Example

These commands enable and enter the address family mode for IPv4 unicast.
switch(config)#router isis Osiris
switch(config-router-isis)#address-family ipv4 unicast 
switch(config-router-isis-af)#

Enabling IS-IS on a Specified Interface

After enabling IS-IS globally, enable it on an interface with the isis enable command.

Example

These commands enable IS-IS on interface ethernet 4.
switch(config-router-isis)#interface ethernet 4
switch(config-if-Eth4)#isis enable Osiris

Configuring IS-IS Optional Global Parameters

Setting the Router Type

The is-type command sets the routing level for an IS-IS instance.

Example

These commands specify level-2 for the IS-IS instance.
switch(config)#router isis Osiris
switch(config-router-isis)#is-type level-2
switch(config-router-isis)#

Configuring Redistribution of Connected or Static Non-ISIS Routes

The redistribute (IS-IS) command configures redistribution of connected or static non-ISIS routes.

Example

These commands redistribute connected routes into the IS-IS domain.
switch(config)#router isis Osiris
switch(config-router-isis)#redistribute connected
switch(config-router-isis)#

Configuring Redistribution of Connected or Static non-ISIS Routes into Level-1 or Level-2

Non-ISIS routes can be exported into Level-1, Level-2, or both using a route map. By default, the routes are exported only to Level-2; to export to Level-1 or to both levels, configure the route map using the set isis level command. The Level-1 or Level-2 routes can also be filtered using the route maps match statement. The route map is then used when redistributing routes in ISIS with the redistribute (IS-IS) command.

Use the show isis database detail command to make sure that the route shows up in the exported level.

Examples
  • The following commands configure a route map called rm to set the IS-IS level to Level-1, then use it to redistribute connected routes.
    switch(config)#route-map rm
    switch(config-route-map-rm)#set isis level level-1
    switch(config-route-map-rm)#router isis osiris
    switch(config-router-isis)#redistribute connected route-map rm
    switch(config-router-isis)#
  • The following command displays IS-IS database information and confirms that the level has been set to Level-1.
    switch#show isis database detail
    ISIS Instance: inst1 VRF: default
     ISIS Level 1 Link State Database
     LSPID Seq Num Cksum Life IS Flags
     1111.1111.1001.00-00 10 63306 751 L2 <>
     NLPID: 0xCC(IPv4) 0x8E(IPv6)
     Area address: 49.0001
    <-------OUTPUT OMITTED FROM EXAMPLE-------->

Configuring Redistribution of BGP Routes into ISIS

The redistribute bgp route-map command redistributes the BGP routes from the specified route map into IS-IS. Only one route map can be specified; reissuing the command overrides any previous configuration.

The no redistribute bgp and default redistribute bgp commands disable BGP route redistribution from the specified domain by removing the redistribute bgp statement from running-config.

The command is available in both router IS-IS configuration mode and the address-family submode. The command is rejected if configured in both modes at the same time. Issuing the no or default command in router IS-IS configuration mode has no effect on redistribution configured in the address-family submode.

Note: If the command is configured in an address-family submode, it only redistributes routes from that address family. If it is configured in router-ISIS mode, it applies to all enabled address families.
Examples
  • These commands redistribute IPv4 BGP routes from the route map called bgp-to-isis-v4 into the ISIS domain.
    switch(config)#router isis 1
    switch(config-router-isis)#address-family ipv4
    switch(config-router-isis-af)#redistribute bgp route-map bgp-to-isis-v4
    switch(config-router-isis-af)#
  • These commands redistribute all BGP routes from the route map bgp-to-isis into ISIS.
    switch(config)#router isis 1
    switch(config-router-isis)#redistribute bgp route-map bgp-to-isis

Setting the Overload Bit

The set-overload-bit command used without the on-startup option, informs other devices not to use the local router to forward transit traffic. When used with the on-startup option, the overload bit is set for the interval specified after startup.

In scenarios when Border Gateway Protocol (BGP) routes are resolved using an Interior Gateway Protocol (IGP), if the transit router reboots and becomes available again, the IGP will consider the transit router as an optimal path again. After rebooting, the transit router will blackhole traffic until the transit router learns the external destination reachability information via BGP.

Examples
  • These commands configure the switch and sets the overload bit to 120 seconds after startup.

    switch(config)#router isis Osiris
    switch(config-router-isis)#set-overload-bit on-startup 120 
    switch(config-router-isis)#
  • These commands configure the overload bit until BGP converges. If BGP fails to converge within the set timeout default period, then the overload bit gets cleared.
    switch(config)#router isis Osiris
    switch(config-router-isis)#set-overload-bit on-startup wait-for-bgp
    switch(config-router-isis)#set-overload-bit on-startup wait-for-bgp timeout 750
    switch(config-router-isis)#

Configuring IS-IS MD5 Authentication

To configure authentication for the IS-IS instance causing LSPs, CSNPs and PSNPs to be authenticated, use the authentication mode and authentication key commands. To configure authentication on the interface, causing IS-IS Hellos to be authenticated, use the isis authentication mode and isis authentication key commands on the interface.

Two forms of authentication are supported by the IS-IS routing protocol: Clear-text authentication and MD5 authentication. The difference between the two forms of authentication is in the level of security provided. In the case of clear-text authentication, the password is specified as text in the authentication TLV, making it possible for an attacker to break authentication by sniffing and capturing IS-IS PDUs on the network. Arista recommends using the MD5 authentication.

HMAC MD5 authentication provides much stronger authentication by computing the message digest (on the IS-IS PDU contents) using the secret key to produce a hashed message authentication code (HMAC). Different modes of authentication can be specified on the interface, which authenticates IIH PDUs (IS-IS hello PDUs), and globally in the router IS-IS mode, in which the LSPs, CSNPs and PSNPs are authenticated. Area-wide and domain-wide authentication can be specified for L1 and L2 routers respectively.

Example
  • These commands configure authentication for the IS-IS instance causing LSPs, CSNPs and PSNPs to be authenticated.
    switch(config)#router isis 1
    switch(config-router-isis)#authentication mode md5
    switch(config-router-isis)#authentication key secret
    switch(config-router-isis)#
  • These commands configure authentication on the interface causing IS-IS Hellos to be authenticated.
    switch(config)#interface Ethernet 3/6
    switch(config-if-Et3/6)#isis authentication mode text
    switch(config-if-Et3/6)#isis authentication key 7 cAm28+9a/xPi04o7hjd8Jw==
    switch(config-if-Et3/6)#

To maximize interoperability, Arista recommends using the same key in both interface mode and in the router isis mode.

Setting the SPF Interval

The SPF timer interval defines the maximum interval between two successive SPF calculations. IS-IS runs SPF calculations following a change in the network topology or the link-state database. The spf-interval command defines the following intervals:

  • Maximum wait interval: The maximum time a switch will wait before running an SPF after a topology change.
  • Initial wait interval: In a network that has been stable throughout the hold interval, this interval defines the initial wait time of a switch for performing an SPF calculation after a topology change. As several link-state updates must be sent after a topology change, the initial wait interval allows the network to settle before a switch computes an SPF. If the topology changes during an initial wait interval, an SPF is calculated after the initial wait interval expires and no further changes are made to throttle timers.
  • Hold time: This interval delays SPF calculations during network instability. If the topology changes during a hold time, an SPF is computed when the hold time expires. Subsequent hold intervals are doubled up to the configured maximum wait interval for continuous topology changes. If the next topology change occurs after the hold interval expires, the hold interval is reset to its configured value and the SPF is computed after the initial wait interval.
    Note: EOS does not support configuring topology-specific SPF timers in multi-topology deployments and IS-IS level-specific SPF timers.

Example

This command configures maximum wait interval, initial wait interval, and hold time to 10 seconds, 2000 ms, and 1000 ms respectively.

switch(config)#router isis inst1
switch(config-router-isis)#spf-interval 10 2000 1000

Configuring IS-IS Segment Routing Global Adjacency-SID

IS-IS Segment Routing (SR) supports global adjacency SIDs for point-to-point interfaces. The adjacency SID is configured as an index using the adjacency-segment command.

Global adjacency segments are represented using an index instead of actual MPLS labels. The index is an offset into the Segment Routing Global Block (SRGB) advertised by a router, resulting in an MPLS label. The default value of SRGB in EOS is Base: 900000 and Size: 65536.

The same index may be used to configure multiple interfaces so that MPLS forms an ECMP group, and the same index may be applied to IPv4 and IPv6 adjacencies.

Example

  • In this example, the global adjacency is configured on a point-to-point interface Ethernet Et1, with an index value 10.
    switch(config-if-Et1)#adjacency-segment ipv4 p2p index 10 global
Displaying Adjacency SID Information

The command show isis segment-routing adjacency-segments displays the global adjacency SID value and other related information.

Examples
  • In this example an interface is configured as follows:
    interface Ethernet1
     ip address 1.1.1.1/24
     ipv6 address 1000::1/64
     isis enable isis1
     isis network point-to-point
     adjacency-segment ipv4 p2p index 1 global
     adjacency-segment ipv6 p2p index 2 global
  • The show output for the above interface configuration:
    Switch#show isis segment-routing adjacency-segments
    
    System ID: 1000.0000.0002                       Instance: isis1
    SR supported Data-plane: MPLS                   SR Router ID: 1.1.1.4
    Adj-SID allocation mode: SR-adjacencies
    Adj-SID allocation pool: Base: 100000     Size: 16384
    Adjacency Segment Count: 2
    Flag Descriptions: F: Ipv6 address family, B: Backup, V: Value
                      L: Local, S: Set
    
    Segment Status codes: L1 - Level-1 adjacency, L2 - Level-2 adjacency, P2P - 
    Point-to-Point adjacency, LAN - Broadcast adjacency
    
    Locally Originated Adjacency Segments
    Adj IP Address     Local Intf  SID     SID Source   Flags                 Type        
    -----------------  ----------  ------  -----------  ---------------       -------
    1.1.1.2            Et1         1       Configured    F:0 B:0 V:0 L:0 S:0  P2P L1
    fe80::1:ff:fe65:0  Et1         2       Configured    F:1 B:0 V:0 L:0 S:0  P2P L1
    
    
    Received Global  Adjacency Segments
    SID              Originator             Neighbor          Flags     
    ---------        --------------------   ----------------  ---------
        0                 rtrmpls1          1000.0000.0002     F:0 B:0 V:0 L:0 S:0

Enabling Logging for Peer Changes

The log-adjacency-changes (IS-IS) command configures the switch to send syslog messages when it detects IS-IS neighbor adjacency state changes.

Example

These commands configure the switch to send a Syslog message when a neighbor goes up or down.
switch(config)#router isis Osiris
switch(config-router-isis)#log-adjacency-changes
switch(config-router-isis)#

Setting the IS-IS hostname

The is-hostname command configures the use of a human-readable string to represent the symbolic name of an IS-IS router. It also changes the output of IS-IS show commands, to show the IS-IS hostname in place of system IDs if the corresponding IS-IS hostname is known. However, syslogs still use IS-IS system IDs and not the IS-IS hostname.

By default if theres a hostname configured on the switch, it is used as the IS-IS hostname. It is also possible to deconfigure an assigned hostname for IS-IS using the no is-hostname command. When the IS-IS hostname is removed, the switch goes back to using the switchs hostname as the IS-IS hostname.

Examples
  • These commands configure the IS-IS hostname to the symbolic name ishost1 for the IS-IS router.
    switch(config)#router isis inst1
    switch(config-router-isis)#is-hostname ishost1
    switch(config-router-isis)#
  • These commands unconfigure the IS-IS hostname of the symbolic name ishost1 for the IS-IS router.
    switch(config)#router isis inst1
    switch(config-router-isis)#no is-hostname ishost1
    switch(config-router-isis)#

Configuring IS-IS Multi-Topology

The multi-topology command configures IS-IS Multi-Topology (MT) support (disabled by default), enabling an IS-IS router to compute a separate topology for IPv4 and IPv6 links in the network. With MT configured, not all the links in a network need to support both IPv4 and IPv6. Some can support IPv4 or IPv6 individually. The IPv4 SPF will install IPv4 routes using the IPv4 topology, and similarly, the IPv6 SPF will install IPv6 routes using the IPv6 topology. Without MT support, all links in an IS-IS network need to support the same set of address families.

When MT is enabled, and each link has a separate IPv4 metric and IPv6 metric.

The isis ipv6 metric command configures the IPv6 metric.

The isis multi-topology command configures the IPv4 or IPv6 address family individually on an interface with both IPv4 and IPv6 addresses.

The address families that are enabled on an interface are based on the global address families enabled in router IS-IS configuration mode, and the addresses configured on the interface. To enable a particular address family on an interface, it needs to have an address configured in that address family. In the case where both IPv4 and IPv6 address families are enabled in router IS-IS configuration mode, then if an interface has IPv4 and IPv6 addresses, both IPv4 and IPv6 address families are enabled on that interface. In the case of an interface with only an IPv4 address family, the IPv4 address family is enabled on that interface. Where an interface only has an IPv6 address family, the IPv6 address family is enabled on that interface. Finally, where only the IPv6 address family is enabled in router IS-IS config mode and MT is enabled, then the IPv6 address family is enabled on all interfaces which have an IPv6 address configured.

Examples
  • These commands configure MT for the IS-IS router.
    switch(config)#router isis 1
    switch(config-router-isis)#address-family ipv6 unicast
    switch(config-router-isis-af)#multi-topology
    switch(config-router-isis-af)#
  • These commands unconfigure MT for the IS-IS router.
    switch(config)#router isis 1
    switch(config-router-isis)#address-family ipv6 unicast
    switch(config-router-isis-af)#no multi-topology
    switch(config-router-isis-af)#
  • These commands configure the IPv6 metric.
    switch(config)#interface Ethernet 5/6
    switch(config-if-Et5/6)#isis ipv6 metric 30
    switch(config-if-Et5/6)#
  • These commands configure the IPv4 address family on an interface with both IPv4 and IPv6 addresses.
    switch(config)#interface Ethernet1
    switch(config-if-Et1)#isis multi-topology address-family ipv4 unicast
    switch(config-if-Et1)#
  • These commands configure the IPv6 address family on an interface with both IPv4 and IPv6 addresses.
    switch(config)#interface Ethernet1
    switch(config-if-Et1)#isis multi-topology address-family ipv6 unicast
    switch(config-if-Et1)#
  • These commands configure both the IPv4 and IPv6 address families on an interface.
    switch(config)#interface Ethernet1
    switch(config-if-Et1)#no isis multi-topology address-family unicast
    switch(config-if-Et1)#

Configuring Optional IS-IS Interface Parameters

Setting the Hello Packet Interval

The isis hello-interval command sets the time interval between the hello packets that maintain an IS-IS adjacency.

Example

These commands configure a hello interval of 60 seconds for interface ethernet 4.
switch(config)#interface ethernet 4
switch(config-if-Et4)#isis hello-interval 60 
switch(config-if-Et4)#

Configuring the Hello Multiplier for the Interface

The switch maintains the adjacency by sending/receiving hello packets. When receiving no hello packets from the peer within a time interval, the local switch considers the neighbors invalid.

The isis hello-multiplier command calculates the hold time announced in hello packets by multiplying this number with the configured isis hello-interval.

Example

  • These commands configure a hello multiplier of 5 for interface ethernet 4.
    switch(config)#interface ethernet 4
    switch(config-if-Et4)#isis hello-interval 60
    switch(config-if-Et4)#isis hello-multiplier 5
    switch(config-if-Et4)#

Configuring the IS-IS Metric

The isis metric command sets the cost for sending information over a specific interface. At present only wide metrics are supported.

Example

These commands configure a metric cost of 30 for sending information over interface ethernet 5.

switch(config)#interface ethernet 5
switch(config-if-Et5)#isis metric 30
switch(config-if-Et5)#

Setting the LSP Transmission Interval

The isis lsp tx interval command configures the minimum interval between successive LSP transmissions on an interface.

Example

This command sets the LSP transmission interval on interface interface ethernet 5 to 50 milliseconds.
switch(config)#interface ethernet 5
switch(config-if-Et5)#isis lsp tx interval 50
switch(config-if-Et5)#

Setting the IS-IS Priority

The isis priority command determines which device will be the Designated Intermediate System (DIS). The device with the highest priority on the LAN will become the DIS.

Example

These commands configure a device priority of 60 on interface interface ethernet 5.
switch(config)#interface ethernet 5
switch(config-if-Et5)#isis priority 60
switch(config-if-Et5)#

Configuring an Interface as Passive

A passive IS-IS interface does not send or receive IS-IS packets and will not form adjacencies, but is still included in LSP advertisements, making its IP address visible to the IS-IS domain.To configure an IS-IS interface as passive, use the isis passive command in interface configuration mode or the passive (IS-IS) command in router IS-IS configuration mode.

Examples
  • These commands configure Ethernet interface 10 as a passive interface.
    switch(config)#interface ethernet 10
    switch(config-if-Etl0)#isis passive
    switch(config-if-Etl0)#
  • These commands also configure Ethernet interface 10 as a passive interface.
    switch(config)#router isis Osiris
    switch(config-router-isis)#passive ethernet 10
    switch(config-router-isis)#

Configuring BFD support for IS-IS for IPv4

The isis bfd and bfd all-interfaces commands configure Bidirectional Forwarding Detection (BFD). BFD is supported for both IS-IS IPv4 and IPv6 routes.

Examples
  • These commands enable BFD (for the IPv4 address family) for all the interfaces on which IS-IS is enabled. By default, BFD is disabled on all interfaces.
    switch(config)#router isis 1
    switch(config-router-isis)#address-family ipv4
    switch(config-router-af)#bfd all-interfaces
    switch(config-router-af)#
  • These commands enable BFD on an IS-IS interface.
    switch(config)#interface Ethernet 5/6
    switch(config-if-Et5/6)#isis bfd
    switch(config-if-Et5/6)#

Configuring IS-IS Segment Routing

Global IS-IS Segment Routing (IS-IS SR) commands are accessed in Segment-Routing MPLS mode, under the router IS-IS configuration mode. Interface-specific IS-IS SR commands are accessed in interface configuration mode.

Starting the MPLS Agent

The Routing Information Base (RIB) or IS-IS agent provides IS-IS segment routing, but the actual installation of LFIB entries pertaining to SR information provided by IS-IS is handled by the MPLS agent in EOS, which is disabled by default. To enable the MPLS agent, use the following commands.

Note: IP(v6) routing must be enabled as a prerequisite.

Example

The following commands enable IP routing and the MPLS agent on the switch.
switch(config)#ip routing
switch(config)#mpls ip
switch(config)#

Enabling IS-IS SR

By default, IS-IS SR is disabled. You must enable it explicitly by issuing theno form of theshutdown (IS-IS SR) command in Segment-Routing MPLS configuration mode.

Example

The following commands enable IS-IS SR.
switch(config)#router isis instance1
switch(config-router-isis)#segment-routing mpls
switch(config-router-isis-sr-mpls)#no shutdown
switch(config-router-isis-sr-mpls)#

Disabling IS-IS Segment Routing

To administratively disable IS-IS SR, issue the shutdown (IS-IS SR) command in Segment-Routing MPLS configuration mode. To disable isis sr and delete all isis sr configuration, issue the no segment-routing mpls command in router isis configuration mode.

Example

  • The following commands administratively disable router isis.
    switch(config)#router isis instance1
    switch(config-router-isis)#segment-routing mpls
    switch(config-router-isis-sr-mpls)#shutdown
    switch(config-router-isis-sr-mpls)#
  • The following commands disable router isis and delete all router isis configuration.
    switch(config)#router isis instance1
    switch(config-router-isis)#no segment-routing mpls
    switch(config-router-isis)#

SRGB (Segment Routing Global Range)

The global segments such as Prefix-SID, Node-SID, Proxy-node-SID are represented using indices of actual MPLS labels. These indices are offset on the SRGB advertised by a router to derive the respective MPLS label. The default value of SRGB in EOS is Base: 900000, Size: 65536. In other words, the labels that any global segment could represent is between 900000-965535. The MPLS label range is categorized and reserved into pools based on the applications using these labels. The default values of label ranges in these pools are:

  • Dynamic Global Range--(100000) (262144)
  • IS-IS SR Global Range -- (900000) (65536)
  • Static Global Range -- (16) (99984)
Note: SRGB can be configured to fit in different MPLS ranges as long as it does not fall under an MPLS range already assigned for usage by other applications.
Example
switch(config)#mpls label range isis-sr 900000 65536

IS-IS Maximum LSP Size

The IS-IS maximum LSP size provides the ability to configure the maximum LSP size that the IS-IS protocol accepts and sends.The default value of LSP size is 9000. The lsp size maximum command configures maximum size of an LSP that is sent or received. The default LSP maximum size is 9000. The minimum value is 512.

Example
switch(config)#lsp size maximum 400
The no lsp size maximum and default lsp size maximum commands remove the specified lsp size maximum command from running-config.
switch(config)#no lsp size maximum
switch(config)#default lsp size maximum

Configuring Node-SID

Node segments are indices associated with routers within an IS-IS SR domain. This is done by associating node-segments with prefix mask length /32 (IPV4) or /128 (IPV6) addresses. Node segments are carried as sub-TLVs (type-length-value) in IP reachability TLVs for the prefixes with which these segments are associated. Node segments are configured on IS-IS enabled Loop-back interface(s) as shown in the example below.

Examples
  • The following commands are used to associate a node-segment with an IPv4 address.
    switch(config)#int loopback 1
    switch(config-if-Lo1)#ip address 21.1.1.1/32
    switch(config-if-Lo1)#node-segment ipv4 index 5
  • The following commands are used to associate a node-segment with an IPv6 address.
    switch(config)#int loopback 1
    switch(config-if-Lo1)#ipv6 add 2000::24/128
    switch(config-if-Lo1)#node-segment ipv6 index 5
  • The following example shows a warning thrown at the CLI when a /32 or /128 address is not configured on the interface.
    switch(config)#int loopback 1
    switch(config-if-Lo1)#ip address 21.1.1.1/24
    switch(config-if-Lo1)#node-segment ipv4 index 1
    ! /32 IPv4 address is not configured on the interface
  • The following command removes the node-segment from IS-IS SR from an interface.
    switch(config-if-Lo1)#no node-segment ipv4 index 1

Configuring Prefix-SIDs

Prefix segments are associated with any IS-IS prefix a router is originating an IP Reachability TLV for. These segments are carried as sub-TLVs in IP Reachability TLVs of the prefixes with which these segments are associated. Prefix segments are configured under segment-routing MPLS configuration mode in IS-IS.

Note: The configured prefix segment is effective, only if, the prefix for which a prefix-SID configured becomes a part of IS-IS by enabling IS-IS on interfaces, or by redistribution from other protocols etc.

Example

The following commands are used to associate a prefix segment with an IPv4 address with index value of 50.
switch(config)#router isis instance1
switch(config-router-isis)#segment-routing mpls
switch(config-router-isis-sr-mpls)#prefix-segment 1.1.1.0/24 index 50

Configuring Proxy-Node SIDs

Node segments represent a device (node) by attaching a segment (index) with a /32, /128 prefix which generally is configured on a loopback interface. There are routers which do not support segment routing, and there might be a situation where it is required to assign node identifiers on such routers. To overcome this shortfall, a router that supports IS-IS SR is made to proxy by configuring a proxy-node-SID for a IS-IS prefix originating from the router that does not support IS-IS SR.

Example

A proxy-node SID associates a /32 or a /128 route with an SID as shown below.
switch(config)#router isis instance1
switch(config-router-isis)#segment-routing mpls
switch(config-router-isis-sr-mpls)#proxy-node-segment 1.1.1.0/32 index 50

Although the general use case is to configure a proxy node segment on a router that is not originating the prefix with which we want to associate the proxy-node SID, it is not prohibited to configure one for self-originated prefixes.

Configuring proxy-node-SIDs enables a router to send out a Binding-SID TLV with details pertaining to the prefix and SID.

Note: A Binding-SID can carry a range of prefixes and an associated range of SIDs, but at present the EOS does not support to configure such ranges with one binding segment TLV in IS-IS SR. However, we do process ranges of prefixes and SIDs if received from devices that support such configurations.

Configuring Anycast-SID

An Anycast-SID is a prefix segment that identifies a set of routers and not a specific router. It enforces the ECMP-aware shortest-path forwarding towards the closest node of the anycast set.

An example of such an anycast group could be a set of routers A1, A2, A3, and A4 where at least one router of A1, A2, A3, and A4 advertises the prefix SID corresponding to the anycast address (which can be a prefix originating on all of A1, A2, A3 and A4 a loop-back address, maybe).

In general use case, all the routers of the anycast group would have the same prefix-SID configured for the anycast IP address present on them.

Note: That for Anycast-SID to work as expected, the SRGB on the members of the anycast group should be same.

Configuring router-ID

A router that support IS-IS SR need to advertise its SR data-plane capability and the range of MPLS label values it uses for segment routing, this is advertised by inserting SR-Capability sub-TLV in the Router Capabilities TLV.

A Router Capability TLV is now sent in IS-IS LSPs when Segment routing is enabled and it is necessary for a Router Capability TLV to carry a router-ID. This router-ID could be configured in EOS under the segment routing MPLS configuration mode. If no router-ID is configured, the router automatically picks up the highest IPv4 address configured on the router for an router-ID.

Configuring IS-IS Static Adjacency SID

Adjacency segments for IS-IS adjacencies are statically configured on the switch, so that these values are preserved even when the switch restarts. Static adjacency segments are configured per address family on any interface (including Port-Channel, VLANs and SVIs). They are configured and advertised as labels.

These are the few points to be considered while configuring the static adjacency SIDs:
  • The same label can be configured on multiple interfaces so that MPLS can form ECMP, the same value can be applied to IPv4 and IPv6 adjacency.
  • Static adjacency SID is applied only to p2p interface, and has local scope. When interface type changes to LAN, then dynamic adjacency SID is assigned.
  • When Static adjacency SIDs are configured, then simply replace dynamic adjacency SIDs which are advertised to other routers and installed in the local LFIB.
  • Static adjacency SID is applied regardless of Adjacency Segment Allocation Mode.
  • When Static adjacency SID is disabled, then normal rules for dynamic adjacency SID is applied (it automatically applies a value based on Adjacency Segment Allocation Mode as described in IS-IS Segment Routing TOI document).

Example

switch(config-if-Et1)#adjacency-segment ipv4 p2p index 50 global

They can be a label (local) or index (global) and we can assign multiple adjacency segments per link.

Where label-value must be within the SR Local Block (SRLB) that can be found in the output of show mpls label range command as shown.

Start     End       Size      Usage
------------------------------------------------
0         15        16        reserved
16        99999     99984     static mpls
100000    362143    262144    free (dynamic)
362144    899999    537856    unassigned
900000    965535    65536     isis-sr
900000    965535    65536     bgp-sr
965536    1031071   65536     srlb
1031072   1036287   5216      unassigned
1036288   1048575   12288     l2evpn

Configuring Adjacency Segment Label Range

Adjacency Segments are MPLS labels assigned to IS-IS adjacencies.These labels are shared with other routers in the domain by adding them in adjacency-SID sub-TLVs which are inserted in neighbor Reachability TLVs in IS-IS.

The MPLS labels (adjacency segments) are incrementally allocated to adjacencies, as the transition to Up state, from a adjacent set of MPLS labels pre-allocated by MPLS agent. This label range extends from 100000 to 116383 (base: 100000, size: 16384) by default. This could be changed by the following configuration:

Example

switch(config)#mpls label range dynamic 200000 131072

The dynamic label pool is shared between LDP and IS-IS SR Adjacency Segments.

Configuring Adjacency Segment Allocation Mode

Adjacency Segments are allocated to all IS-IS adjacencies based on the IS-IS routers that have advertised IS-IS SR capability or to none of the adjacencies. The command adjacency-segment allocation is used to configure this under the segment-routing mpls configuration mode.

The default behavior is to allocate adjacency segments to adjacencies of SR supporting devices.

Example

switch(config-router-isis-sr-mpls)#adjacency-segment allocation sr-peer

Adjacency Segment Persistence across Link Flaps

Adjacency segments are allocated to IS-IS adjacencies based on configured adjacency segment allocation mode mentioned above.

If an adjacency that has been allocated label L goes down, L is reserved for this adjacency for a duration of 3600 seconds from the time of the adjacency down event. Only the adjacency that owned this label before going down could reclaim label L in this duration.

Troubleshooting IS-IS Segment Routing

  • The show tech-support ribd command has a section starting with the string SR Book Keeper which has extensive information on state of IS-IS SR on the router.
  • In-case, if IS-IS SR is configured but SR related TLVs/sub, but, TLVs are not being sent in IS-IS LSPs.
    • Ensure that MPLS has been enabled (MPLD IP) enabled.
    • Check if segment routing is administratively shut down.
    • A segment might have been configured for a prefix not yet being advertised in IS-IS.
  • In case, if Adjacency Segments are not being advertised.
    • Check if the adjacency segment mode is correctly set.
    • Adjacency Mode is set to all SR supported interfaces (default setting) and the peer does not support SR.
  • Generally, it is good to not have same prefix with different indices or same index with different prefixes. There are CLI prohibitions that ensure that a router is not sending out conflicting sets of prefixes and associated SIDs. As there is possibility of receiving conflicting prefix-segments from other devices, there are ways to resolve the following three types of conflicts: prefix+SID conflict, SID conflict and prefix conflict.
    • Prefix+SID Conflict: When there are two prefix segments which have both the prefix and SID have same values, the one from the higher system ID is chosen for LFIB processing.
    • Prefix Conflict: If the two prefix segments which have same Prefix are from two different system than the one from higher system ID is chosen. If they are originated from same system ID than we choose the prefix segment of smaller SID.
    • SID Conflict: If the two prefix segments which have same SID are from two different system than the one from higher system ID is chosen. If they are originated from same system than the one which is of smaller prefix length is chosen. If prefix length is also same than the one with smaller address is chosen.

For a given prefix, if both a proxy-node segment and prefix-SID are received, the prefix-SID advertised is preferred while the proxy-node segment is ignored.

The show tech-support ribd displays detail information about IS-IS SRs internal state, and more information on conflicts and chosen active segments could be found under the SR Book Keeper section of show tech-support ribd command as shown.

Received Prefix Segments:
------------------------------------------------------------------
 Prefix    | Value | Index/Label | Type   | SystemID      | spfgen
 * - Active, # - Duplicate pfx, + - duplicate SID 
-------------------------------------------------------------------
*1.0.3.0/24    3      Index        Prefix   1111.1111.1002   0
*1.0.5.1/32    0      Index        Node     1111.1111.1002   0
*1.0.6.1/32    2      Index        Node     1111.1111.1003   39
*1.0.7.1/32    14     Index        Node     1111.1111.1001   39
#1.0.7.1/32

10 Index Proxy 1111.1111.1003 39

Configuring Redistribution of DHCP for IS-IS Agent (IPv6)

The redistribute dhcp command redistributes DHCPv6 routes in IS-IS when using multi-agent routing protocol mode.

The redistribute dhcp command enables DHCP route redistribution in IS-IS when using the multi-agent routing protocol mode.
  • These commands redistribute IPv6 DHCP routes into the ISIS domain.
    switch(config)#router isis 1
    switch(config-router-isis)#address-family ipv6
    switch(config-router-isis-af)#redistribute dhcp
    switch(config-router-isis-af)#
  • The following command shows the DHCPv6 routes distributed into IS-IS.
    switch(config)#show isis database detail
    IS-IS Instance: inst1 VRF: default
      IS-IS Level 1 Link State Database
        LSPID                 Seq Num   Cksum  Life  IS Flags
        1111.1111.1001.00-00  10        19778  1101  L1 <>
          ...
          Reachability (MT-IPv6): 3ffe:701:ffff:101::10/128 Metric: 0 Type: 1 Up
          ...

Disabling IS-IS

An IS-IS instance can be shut down globally or can be disabled on individual interfaces.

The shutdown (IS-IS) command shuts down an IS-IS instance globally.

Example

These commands disable IS-IS globally without modifying the IS-IS configuration.
switch(config)#router isis Osiris
switch(config-router-isis)#shutdown
switch(config-router-isis)#

The no isis enable command disables IS-IS on an interface.

Example

These commands disable IS-IS on interface interface ethernet 4.
switch(config-router-isis)#interface ethernet 4
switch(config-if-Eth4)#no isis enable

Configuring IS-IS Graceful Restart (GR)

By default, IS-IS graceful restart is disabled. Use the graceful-restart command to configure graceful restart on an IS-IS router. By default IS-IS graceful-restart-helper functionality is enabled, and to disable it use no graceful-restart-helper command.

Examples

In this example IS-IS graceful restart is configured with t2 wait time of 30 seconds for level-1 routes.
switch(config)#router isis 1
switch(config-router-isis)#graceful-restart t2 level-1 30

t2 is the maximum wait time for the LSP database to synchronize (SPF computation is not done while t2 is running). t2 can be configured for either Level-1 or Level-2 through the CLI. The default value is 30 seconds, and the allowed configuration range is 5 to 300 seconds.

Example

In this example an ISIS graceful restart is configured with restart-hold-time of 50 seconds.
switch(config)#router isis 1
switch(config-router-isis)#graceful-restart restart-hold-time 50

In case of a planned restart, the hold time advertised by the IS-IS router prior to restart should be greater than the time for which the router is expected to be offline. Otherwise, neighboring routers will bring down the adjacency before the restarting router has a chance to send a restart request in its hello packet, which may result in traffic loss.

In case of ASU2, the IS-IS router instance will advertise a hello hold time of restart-hold-time on those interfaces for which the configured hold time is less than restart-hold-time. This is done just before the router restarts.

Note: Once the router has restarted, the routers advertised hello hold time will depend on the hello-interval and hello-multiplier configuration on each interface as before. By default, the restart-hold-time is disabled.

For Graceful Restart to be successful, the hold time advertised by the router should be greater than the time it takes for Graceful Restart to complete. If the restarting router is DIS, hold time advertised is 1/3rd of the configured value (default is 9s). We recommend increasing the hold time for the DIS to a higher value before a planned restart; otherwise, it may result in traffic loss.

TI-LFA FRR using IS-IS Segment-Routing Configuration

Configuring Link or Node Protection on a Specific Interface

To enable link or node protection for node segments and Adjacency segments learned on a specific IS-IS interface, use the following command in the interface configuration mode.

switch(config-if-Et1)#[no|default] isis fast-reroute ti-lfa mode {link-protection|node-protection|disabled} [level-1|level-2]

The interface TI-LFA configuration inherits the address-family sub-mode configuration by default.

On an L1-L2 router, the [level-1|level2] optional keyword in both the router IS-IS address-family sub-mode and interface configuration mode CLIs is used to restrict protection to node segments and Adjacency segments learned through either Level-1 or Level-2 topologies only.

Configuring a Local LFIB Convergence Delay for Protected Node or Adjacency Segments

The Point of Local Repair (PLR) switches to the TI-LFA backup path on link failure or BFD neighbor failure but switches back to the post-convergence path once the PLR computes SPF and updates its LFIB. This sequence of events can lead to micro-loops in the topology if the PLR converges faster than other routers along the post-convergence path. So a configuration option is provided to apply a delay, after which the LFIB route being protected by the TI-LFA loop-free repair path will be replaced by the post-convergence LFIB route.

To configure a convergence delay only to LFIB routes that are being protected, the following command is used either in the router IS-IS mode or the router isis address-family sub-mode. A default of 10 seconds is used when using the command without an explicitly specified delay.

switch (config-router-isis-af)#timers local-convergence-delay [delay_in_milliseconds] protected-prefixes

Making Locally-originated Adjacency Segments Backup Eligible

The PLR computes backup paths for an adjacency segment only if the Adjacency SID sub-TLV has the B-flag (backup flag) set.

To set the B-flag in originated Adjacency SID sub-TLVs corresponding to adjacency segments dynamically allocated on the router, the following command is used in the segment-routing mpls sub-mode in the router isis mode.

switch(config-router-isis-sr-mpls)#adjacency-segment allocation [all-interfaces | sr-peers]

To set the B-flag in originated Adjacency SID sub-TLVs corresponding to adjacency segments statically configured on the router, the following command is used in the interface configuration mode.

switch(config-if-Et1)#adjacency-segment [ ipv4 | ipv6 ] p2p [ multiple ][ label label | index index ] backup-eligible

backup-eligible is the newly introduced optional keyword in both the CLIs mentioned above that controls the setting of the B-flag in the Adjacency SID sub-TLV.

Enabling SRLG Protection

To enable SRLG protection on all interfaces, use the fast-reroute ti-lfa srlg command. This command is used in addition to configuring link-protection or node-protection. If SRLG protection is enabled, the backup paths are computed after excluding all the links that share the same SRLG with the active link that is being used by all prefix segments and adjacency segments.

switch(config-router-isis-af)#fast-reroute ti-lfa srlg [strict]

If the optional argument strict is configured, the backup path is only programmed if a backup path that excludes all the SRLGs configured on the primary interface. If the keyword is not provided and an SRLG excluding path is not available, TI-LFA programs the backup path that excluded the maximum number of SRLGs possible.

To selectively disable SRLG protection on an interface, use the isis [ipv4|ipv6] fast-reroute ti-lfa srlg disabled command. This is useful if SRLG protection is enabled globally for all interfaces but needs to be selectively disabled for a specific interface.

switch(config-intf-et1)#isis [ ipv4 | ipv6 ] fast-reroute ti-lfa srlg disabled

Sample Configuration

Figure 2. Sample Configuration

The above topology is used to demonstrate the configuration and show command output. You will see the backup paths that the PLR computes to protect the node segments of R1 and R2, the global adjacency segment on R2, and the local adjacency segment on the vlan 2387 on the PLR.

Here is a snippet of the configuration on the PLR.

switch(config)#interface vlan 2138
switch(config-if-Vl2138)#ip address 10.1.1.1/24
switch(config-if-Vl2138)#isis enable inst1
switch(config-if-Vl2138)#isis metric 11
switch(config-if-Vl2138)#isis network point-to-point

switch(config)#interface vlan2387
switch(config-if-Vl2138)#ip address 10.1.2.1/24
switch(config-if-Vl2138)#isis enable inst1
switch(config-if-Vl2138)#isis network point-to-point  
switch(config-if-Vl2138)#adjacency-segment ipv4 p2p label 965537 backup-eligible  
   
switch(config)#interface vlan2968
switch(config-if-Vl2968)#ip address 10.1.3.1/24
switch(config-if-Vl2968)#isis enable inst1
switch(config-if-Vl2968)#isis network point-to-point
switch(config-if-Vl2968)#isis fast-reroute ti-lfa mode disabled

…

switch(config)#router isis inst1
switch(config-isis)#net 49.0001.1111.1111.1001.00
switch(config-isis)#router-id ipv4 252.252.1.252
switch(config-isis)#is-type level-2
switch(config-isis)#timers local-convergence-delay 5000 protected-prefixes
   !
switch(config-isis)#address-family ipv4 unicast
switch(config-isis-af)#fast-reroute ti-lfa mode node-protection
   !
   
switch(config-isis)#segment-routing mpls
switch(config-isis-sr-mpls)#no shutdown
switch(config-isis-sr-mpls)#adjacency-segment allocation sr-peers backup-eligible
!
end

The protection of anycast segments does not need any new configuration. The above configuration enables protection of anycast segments.

To demonstrate the protection of anycast segments consider the following topology.

Figure 3. Topology Number 2

R1 and R4 are originators of the host prefix 10.10.10.1/32 and advertise prefix segment 900010. This must be configured as a prefix segment and not a node segment.

R1 and R4’s configuration should look similar to the following:

switch(confg)#router isis inst1
switch(config-router-isis)#interface Loopback0
switch(config-if-Lo0)#ip address 10.10.10.1/32
switch(config-if-Lo0)#isis enable inst1
     
!
...
switch(confg)#router isis inst1  
switch(config-router-isis)#segment-routing mpls
switch(config-router-isis-sr-mpls)#prefix-segment 10.10.10.1/32 index 10
!

The prefix in the prefix-segment command must belong to an interface enabled with IS-IS or must be an active route in the RIB of another protocol redistributed into IS-IS.

When the link or node protection is configured on the PLR, then the primary path to the segment 900010 is PLR - R1 and the backup path is PLR - R2 - R3 - R4. In other words, the destination in the backup path is the segment originated by R4 as the segment originated by R1 and is not reachable when link PLR-R1 or the node R1 goes down.

show ip route

When services like LDP pseudowires, BGP LU, L2 EVPN, or L3 MPLS VPN use IS-IS SR tunnels as an underlay, these services are automatically protected by TI-LFA tunnels that protect the IS-IS SR tunnels. The show ip route command displays the hierarchy of the overlay-underlay-TI-LFA tunnels.

 B        2001:db8:3::/48 [200/0]
           via 2002::b00:301/128, IS-IS SR tunnel index 3, label 122697 
		via TI-LFA tunnel index 5, label imp-null(3)      
		via fe80::200:76ff:fe03:0, Ethernet26/1, label imp-null(3)
		backup via fe80::200:76ff:fe01:0, Ethernet30/1, label 900002 900003

IS-IS Dynamic Flooding Configuration

Configure Dynamic flooding using the lsp flooding dynamic command under the router config mode. For example:
switch(config)#router isis Amun
switch(config-router-isis)#net 49.0000.0000.3333.00
switch(config-router-isis)#is-hostname ip3
switch(config-router-isis)#lsp flooding dynamic

Dynamic flooding should be enabled on all routers in the area. To enable Dynamic Flooding on all routers, use the following command:

lsp flooding dynamic [level-1 | level-2]

nolsp flooding dynamic [level-1 | level-2]

default lsp flooding dynamic [level-1 | level-2]

If necessary, the area leader election process can be tuned or disabled with the commands:

area leader [level-1 | level-2] priority 0-255 area leader [level-1 | level-2] disabled

no area leader [level-1 | level-2] priority 0-255 area leader [level-1 | level-2] disabled

default area leader [level-1 | level-2] priority 0-255 area leader [level-1 | level-2] disabled

Limitations

On a sparse topology, Dynamic Flooding is not effective and only adds overhead. Leaf-spine and Clos networks are appropriate dense topologies.

Relax Address-Family Check for IS-IS Adjacency

Address-Family Check for IS-IS creates the adjacency between devices with different address famiies. For example, a router supporting IPv4 and IPv6 is connected to a IPv4 only router, Address-Family Check is verified by comparing the NLPID TLV ( Type #129 ) advertised in IIH hellos exchanged between peers. It is useful in following scenarios.

Incrementally enable IPv6 in an existing IPv4 network

Relaxing the Address-Family Check is useful to gradually add IPv6 support in an IPv4 network, without disturbing the IPv4 connectivity.

IPv4 Controller Peering IPv4/v6 Dual Stack Router

A controller forms an IS-IS adjacency with a router and uses the IS-IS database for topology discovery. If the controller only supports IPv4 IS-IS or only IPv4 tunnels, to relax the Address-Family Check on the dual stack IPv4/v6 router for adjacency is useful in establishment.

Disabling the Address-family check

Under IS-IS instance, configure the following to disable the Address-Family Check during IIH processing.

switch(config-router-isis)#?
   adjacency Configure parameters for adjacency formation
switch(config-router-isis)# adjacency?
   address-family Configure address-family related parameters for adjacency formation
switch(config-router-isis)# adjacency address-family?
   match Configure address-family match check related parameters for adjacency formation
switch(config-router-isis)# adjacency address-family match?
   disabled Relax address-family match check for bringing up adjacency 
switch(config-router-isis)# adjacency address-family match disabled?

Show command

The show isis neighbor detail command displays address family details at each end of the adjacency.
Instance  VRF      System Id   Type Interface       SNPA        State Hold time   Circuit Id
inst1     default  1111.1111.1002   L2   Vlan2116           P2P            UP    24          06
  Area Address(es): 49.0001
  SNPA: P2P
  Router ID: 1.0.0.2
  Advertised Hold Time: 30
  State Changed: 00:04:18 ago at 2020-11-01 22:28:35
  IPv4 Interface Address: 1.0.0.2
  IPv6 Interface Address: none
  Interface name: Vlan2116
  Graceful Restart: Supported
  Segment Routing Enabled
    SRGB Base: 900000 Range: 65536
    Adjacency Label IPv4: 149152
  Supported Address Families: IPv4, IPv6 
  Neighbor Supported Address Families: IPv4
The show isis interface detail command shows the details of supported protocols on the interface and the neighbors connected to it. The state of Address-Family match check is also displayed.
switch(config-router-isis)# show isis interface detail
IS-IS Instance: inst1 VRF: default
  Interface Vlan2116:
    Index: 35 SNPA: P2P
    MTU: 1497 Type: point-to-point
   Supported Address Families: IPv4, IPv4
    Area Proxy Boundary is Disabled
    BFD IPv4 is Disabled
    BFD IPv6 is Disabled
    Hello Padding is Enabled
    Level 2:
      Metric: 10, Number of adjacencies: 1
      Link-ID: 23
      Authentication mode: None
      TI-LFA link protection is enabled for the following IPv4 segments: node segments, adjacency segments
      TI-LFA protection is disabled for IPv6
    Adjacency 1111.1111.1002:
      State: UP, Level: 2 Type: Level 2 IS
      Advertised Hold Time: 30
     Neighbor Supported Address Families: IPv4
     Address Family Match: Disabled
      IPv4 Interface Address: 1.0.0.2
      Areas:
        49.0001

Usage Guidelines

For IPv6 network upgrade, ensure the knob is incrementally configured on a contiguous section of the network, at any point the choice of routers for upgrade should not bisect the upgraded (supporting IPv4/v6) part of the network. All the routers bordering the upgraded network should always have the knob enabled.

When a proper set of router is established, the following steps are carried on each router.
  1. Enable the CLI knob.
  2. Enable IPv6 address family in the IS-IS instance.
  3. Configure IPv6 on all the IS-IS interfaces.

Displaying IS-IS Information

Displaying the Link State Database

To display the link state database of IS-IS, use the show isis database command.

Example

This command displays the IS-IS link state database.
switch#show isis database
ISIS Instance: Osiris
  ISIS Level 2 Link State Database
    LSPID                 Seq Num   Cksum  Life  IS Flags
    1212.1212.1212.00-00  4         714    1064  L2 <>
    1212.1212.1212.0a-00  1         57417  1064  L2 <>
    2222.2222.2222.00-00  6         15323  1116  L2 <>
    2727.2727.2727.00-00  10        15596  1050  L2 <>
    3030.3030.3030.00-00  12        62023  1104  L2 <>
    3030.3030.3030.c7-00  4         53510  1104  L2 <>
switch>

Displaying the Interface Information for the IS-IS Instance

To display interface information related to the IS-IS instance, use the show isis interface command.

Example

This command displays IS-IS interface information.
switch#show isis interface

ISIS Instance: Osiris
  Interface Vlan20:
    Index: 59 SNPA: 0:1c:73:c:5:7f
    MTU: 1497 Type: broadcast
    Level 2:
      Metric: 10, Number of adjacencies: 2
      LAN-ID: 1212.1212.1212, Priority: 64
      DIS: 1212.1212.1212, DIS Priority: 64
  Interface Ethernet30:
    Index: 36 SNPA: 0:1c:73:c:5:7f
    MTU: 1497 Type: broadcast
    Level 2:
      Metric: 10, Number of adjacencies: 1
      LAN-ID: 3030.3030.3030, Priority: 64
      DIS: 3030.3030.3030, DIS Priority: 64
switch>

Displaying IS-IS Neighbor Information

To display general information for IS-IS neighbors that the device sees, use show isis neighbors.

Example

This command displays information for IS-IS neighbors that the device sees.
switch#show isis neighbor
Inst Id   System Id       Type  Interface   SNPA          State  Hold time
10        2222.2222.2222  L2    Vlan20       2:1:0:c:0:0   UP    30
10        1212.1212.1212  L2    Vlan20       2:1:0:d:0:0   UP     9
10        3030.3030.3030  L2    Ethernet30   2:1:0:b:0:0   UP     9
switch>

Displaying IS-IS Instance Information

To display the system ID, Type, Interface, IP address, State and Hold information for IS-IS instances, use the show isis summary command. The command is also used to verify the configured maximum wait interval, initial wait interval, and hold time of SPF timers in IS-IS instances. This command also displays values of the current SPF interval, last Level-1 SPF run, and last Level-2 SPF run.

Example
  • This command displays general information about IS-IS instances.
    switch#show isis summary
    ISIS Instance: Osiris
      System ID: 1010.1040.1030, administratively enabled, attached
      Internal Preference: Level 1: 115, Level 2: 115
      External Preference: Level 1: 115, Level 2: 115
      IS-Type: Level 2, Number active interfaces: 1
      Routes IPv4 only
      Last Level 2 SPF run 2:32 minutes ago
      Area Addresses:
        10.0001
      level 2: number dis interfaces: 1, LSDB size: 1
    switch>
  • This command displays the SPF interval information about IS-IS instances.
    switch(config-router-isis-af)#show isis summary
    
    IS-IS Instance: 1 VRF: default
     System ID: 0000.0000.0001, administratively enabled
     Multi Topology disabled, not attached
     IPv4 Preference: Level 1: 115, Level 2: 115
     IPv6 Preference: Level 1: 115, Level 2: 115
     IS-Type: Level 1 and 2, Number active interfaces: 0
     Routes both IPv4 and IPv6
                               Max wait(s) Initial wait(ms) Hold interval(ms)
     LSP Generation Interval:     5              50               50
     SPF Interval:                2            1000             1000
     Current SPF hold interval(ms): Level 1: 1000, Level 2: 1000
     Last Level 1 SPF run 1 seconds ago
     Last Level 2 SPF run 1 seconds ago
     Authentication mode: Level 1: None, Level 2: None
     Graceful Restart: Disabled, Graceful Restart Helper: Enabled
     Area Addresses:
       49.0001
     level 1: number dis interfaces: 0, LSDB size: 1
     level 2: number dis interfaces: 0, LSDB size: 1

Displaying IS-IS Segment Routing Information

show isis database detail

The show isis database detail command provides a view of LSPDB of different devices in the IS-IS domain. The output displays the TLVs and sub-TLVs that are being self-originated or the ones that have been received from other routers.

Example

switch#show isis database detail
ISIS Instance: inst1 VRF: default
 ISIS Level 2 Link State Database
 LSPID Seq Num Cksum Life IS Flags
 1111.1111.1001.00-00 10 63306 751 L2 <>
 NLPID: 0xCC(IPv4) 0x8E(IPv6)
 Area address: 49.0001
 Interface address: 1.0.7.1
 Interface address: 1.0.0.1
 Interface address: 2000:0:0:47::1
 Interface address: 2000:0:0:40::1
 IS Neighbor : lf319.53 Metric: 10
    LAN-Adj-sid: 100000 flags: [ L V ] weight: 0 system ID: 1111.1111.1002
 IS Neighbor (MT-IPv6): lf319.53 Metric: 10
    LAN-Adj-sid: 100001 flags: [ L V F ] weight: 0 system ID: 1111.1111.1002
 Reachability : 1.0.11.0/24 Metric: 1 Type: 1 Up
    SR Prefix-SID: 10 Flags: [ R ] Algorithm: 0
 Reachability : 1.0.3.0/24 Metric: 1 Type: 1 Up
 Reachability : 1.0.7.1/32 Metric: 10 Type: 1 Up
    SR Prefix-SID: 2 Flags: [ N ] Algorithm: 0
 Reachability : 1.0.0.0/24 Metric: 10 Type: 1 Up
 Reachability (MT-IPv6): 2000:0:0:4b::/64 Metric: 1 Type: 1 Up
    SR Prefix-SID: 11 Flags: [ R ] Algorithm: 0
 Reachability (MT-IPv6): 2000:0:0:43::/64 Metric: 1 Type: 1 Up
 Reachability (MT-IPv6): 2000:0:0:47::1/128 Metric: 10 Type: 1 Up
    SR Prefix-SID: 3 Flags: [ N ] Algorithm: 0
 Reachability (MT-IPv6): 2000:0:0:40::/64 Metric: 10 Type: 1 Up
 Router Capabilities: 252.252.1.252 Flags: [ ]
    SR Capability: Flags: [ I V ]
       SRGB Base: 900000 Range: 65536
 Segment Binding: Flags: [ F ] Weight: 0 Range: 1 Pfx 2000:0:0:4f::1/128
    SR Prefix-SID: 19 Flags: [ ] Algorithm: 0
 Segment Binding: Flags: [ ] Weight: 0 Range: 1 Pfx 1.0.15.1/32
    SR Prefix-SID: 18 Flags: [ ] Algorithm: 0
show isis segment-routing

The show isis segment-routing command displays the summary information on IS-IS SR status.

Example

switch(config)#show isis segment-routing
System ID: 1111.1111.1002               Instance: inst1
SR supported Data-plane: MPLS           SR Router ID: 252.252.2.252
SR Global Block( SRGB ): Base: 900000   Size: 65536
Adj-SID allocation mode: SR-adjacencies
Adj-SID allocation pool: Base: 100000     Size: 16384
All Prefix Segments have    : P:0 E:0 V:0 L:0
All Adjacency Segments have : F:0 B:0 V:1 L:1 S:0
ISIS Reachability Algorithm : SPF (0)
Number of ISIS segment routing capable peers: 3
Self-Originated Segment Statistics:
Node-Segments       : 2
Prefix-Segments     : 2
Proxy-Node-Segments : 0
Adjacency Segments  :

About the Output

The first line of the output shows the IS-IS system ID of this device and the name of the instance with which IS-IS is configured.

The supported data plane is shown against the SR supported Data-plane field whereas the Router ID being advertised in the Router Capability is mentioned in the SR Router ID Field.

The SRGB in use and the MPLS label pool being used for adjacency segment allocation are mentioned in this output. The current adjacency allocation mode which refers to whether we are allocating adjacency segments to all IS-IS adjacencies or only those adjacencies which support SR or None of the adjacencies is shown in the Adj-SID allocation mode field.

Flag contents of All Prefix Segments originated on this router, Flag contents of All Adjacency Segments originated on this router and supported IS-IS Reachability Algorithm have been provided through this command output and they carry the meaning as per the IS-IS SR IETF draft.

This show command provides a statistics related to IS-IS SR in terms of various counters ranging from number of IS-IS SR enabled peers, number of Node-SIDs, prefix-SIDs, proxy-node-segments and adjacency segments being originated on this router in IS-IS.

The show isis segment-routing command also provides information if segment routing has been administratively disabled as shown.

switch(config-router-isis-sr-mpls)#show isis segment-routing
! IS-IS (Instance: inst1) Segment Routing has been administratively shutdown
show isis segment-routing global-blocks

The show isis segment-routing global-blocks command lists the SRGBs in use by all SR supporting devices in IS-IS domain including the SRGB in use by IS-IS SR on this device.

Example

switch#show isis segment-routing global-blocks
System ID: 1111.1111.1002              Instance: inst1
SR supported Data-plane: MPLS          SR Router ID: 252.252.2.252
SR Global Block( SRGB ): Base: 900000  Size: 65536
Number of ISIS segment routing capable peers: 3
SystemId             Base         Size
-------------------- ------------ ----- 
1111.1111.1002        900000      65536
1111.1111.1001        900000      65536
show isis segment-routing prefix-segments

The show isis segment-routing prefix-segments command provides the details of all prefix segments being originated as well the segments received from IS-IS SR speakers in the domain.

Example

switch#show isis segment-routing prefix-segments
System ID: 1111.1111.1002         Instance: inst1
SR supported Data-plane: MPLS     SR Router ID: 252.252.2.252
Node: 2 Proxy-Node: 2 Prefix: 2 Total Segments: 6
Flag Descriptions: R: Re-advertised, N: Node Segment, P: no-PHP
                   E: Explicit-NULL, V: Value, L: Local
Segment status codes: * - Self originated Prefix, L1 - level 1, L2 - level 2
Prefix        SID     Type        Flags                    SystemID        Type
--------------------- ---------   ----------------         --------------------- 
 1.0.7.1/32    2      Node        R:0 N:1 P:0 E:0 V:0 L:0   1111.1111.1001  L1
* 1.0.8.1/32   4      Node        R:0 N:1 P:0 E:0 V:0 L:0   1111.1111.1002  L2
 1.0.11.0/24   10     Prefix      R:1 N:0 P:0 E:0 V:0 L:0   1111.1111.1001  L2
* 1.0.12.0/24  12     Prefix      R:1 N:0 P:0 E:0 V:0 L:0   1111.1111.1002  L2
 1.0.15.1/32   18     Proxy-Node  R:0 N:0 P:0 E:0 V:0 L:0   1111.1111.1001  L2
 1.0.16.1/32   20     Proxy-Node  R:0 N:0 P:0 E:0 V:0 L:0   1111.1111.1003  L2

About the Output

After the usual output header that represents the system ID, instance name, etc and parameters of a router, there is a line depicting prefix segment counters. Each field in this line relates to the number of segments that are present in this routers IS-IS instance. For example, the above example shows that this device has 2 Node Segments (Self originated as well as the ones received from other IS-IS SR devices).

The main section of this show commands output is the section that lists all the prefix segments and related information like prefix, SID, type of segment (Prefix, Node, Proxy-Node), the flag values being carried in the sub-TLVs of these prefix segments and the system ID of the originating router. The Type field will be useful on a IS type level-1-2 router. It shows whether the installed prefix segment is from a level-1 prefix or a level-2 prefix.

show isis segment-routing prefix-segments self-originated

The show isis segment-routing prefix-segments self-originated command output is identical to show isis segment-routing prefix-segments except, the fact that the former lists only self-originated prefix segments.

show isis segment-routing adjacency-segments

The show isis segment-routing adjacency-segments displays list of all the adjacency segments that are being originated by IS-IS SR on a router.

Example

switch#show isis segment-routing adjacency-segments
System ID: 1111.1111.1002           Instance: inst1
SR supported Data-plane: MPLS       SR Router ID: 252.252.2.252
Adj-SID allocation mode: SR-adjacencies
Adj-SID allocation pool: Base: 100000     Size: 16384
Adjacency Segment Count: 4
Adj IP-address     Local     Intf    Label    SID  Source     Flags      Type
-----------------  --------  ------  ------   ---  ---------  ---------  --------
1.0.0.1            Vlan2472  100000  Dynamic  F:0   B:0 V:1    L:1 S:0   LAN L2
1.0.1.2            Vlan2579  100001  Dynamic  F:0   B:0 V:1    L:1 S:0   P2P L2
fe80::1:ff:fe01:0  Vlan2472  100002  Dynamic  F:0   B:0 V:1    L:1 S:0   LAN L2
fe80::1:ff:fe02:0  Vlan2579  100003  Dynamic  F:0   B:0 V:1    L:1 S:0   P2P L2

About the Output

It consists allocation mode, MPLS label pool from which labels would be allocated to adjacencies, total count of adjacency segments allocated so far and the default flag values carried in all adj-SID sub-TLVs originating from this device.

The main section of the output lists all the adjacency segments allocated so far in six columns each pertaining to Adjacency IP address, local interface name, MPLS label value, SID source, flags in the sub-TLV and the type of adj-SID respectively. The type of the adjacency segments depends on the IS-IS type of adjacency and the IS level.

show mpls label ranges

The show mpls label ranges command displays the MPLS label range available on a router is categorized into different pools which cater to different applications running on the router.

The isis-sr refers to the SRGB use-case in IS-IS, and isis (dynamic) refers to the label pool that is used for dynamic allocation of adjacency segments in IS-IS.

Example

switch#show mpls label ranges
Start    End      Size     Usage
-----------------------------------------
0        15       16       reserved
16       99999    99984    static mpls
100000   116383   16384    isis (dynamic)
116384   362143   245760   free (dynamic)
362144   899999   537856   unassigned
900000   965535   65536    isis-sr
show mpls segment-routing bindings

The show mpls segment-routing bindings command displays the local label bindings and label bindings on the peer routers for each prefix that has a segment advertised. Peer ID here represents the IS-IS system ID of the peer.

Example

switch#show mpls segment-routing bindings
1.0.7.1/32
 Local binding: Label: 900002
 Remote binding: Peer ID: 1111.1111.1001, Label: imp-null
 Remote binding: Peer ID: 1111.1111.1003, Label: 900002
1.0.8.1/32
 Local binding: Label: imp-null
 Remote binding: Peer ID: 1111.1111.1001, Label: 900004
 Remote binding: Peer ID: 1111.1111.1003, Label: 900004
1.0.9.1/32
 Local binding: Label: 900006
 Remote binding: Peer ID: 1111.1111.1001, Label: 900006
 Remote binding: Peer ID: 1111.1111.1003, Label: imp-null
show mpls lfib route

The show mpls lfib route command displays the LFIB. Each LFIB entry has In-Label, Out-Label, metric, payload type, nexthop information, etc. fields. The source column depicts the MPLS control plane protocol that is responsible for the label binding that resulted in this LFIB route.

Example

switch#show mpls lfib route
MPLS forwarding table (Label [metric] Vias) - 7 routes
MPLS next-hop resolution allow default route: False
Via Type Codes:
        M - Mpls Via, P - Pseudowire Via,
        I - IP Lookup Via, V - Vlan Via,
        VA - EVPN Vlan Aware Via, ES - EVPN Ethernet Segment Via,
        VF - EVPN Vlan Flood Via, AF - EVPN Vlan Aware Flood Via,
        NG - Nexthop Group Via
Source Codes:
        S - Static MPLS Route, B2 - BGP L2 EVPN,
        B3 - BGP L3 VPN, R - RSVP,
        P - Pseudowire, L - LDP,
        IP - IS-IS SR Prefix Segment, IA - IS-IS SR Adjacency Segment,
        IL - IS-IS SR Segment to LDP, LI - LDP to IS-IS SR Segment,
        BL - BGP LU, ST - SR TE Policy,
        DE - Debug LFIB

 IA 100000 [1]
            via M, 1.0.1.2, pop
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930
 IA 100001 [1]
            via M, fe80::200:eff:fe02:0, pop
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930
 IP 900008 [1]
            via M, 1.0.1.2, swap 900008
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930
 IP 900009 [1]
            via M, fe80::200:eff:fe02:0, swap 900009
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930
show mpls lfib route <label value>

The show mpls lfib route <label value> command provides information relevant to just the label value passed as an extension to the show command.

Example

switch#show mpls lfib route 900008
MPLS forwarding table (Label [metric] Vias) - 7 routes
MPLS next-hop resolution allow default route: False
Via Type Codes:
        M - Mpls Via, P - Pseudowire Via,
        I - IP Lookup Via, V - Vlan Via,
        VA - EVPN Vlan Aware Via, ES - EVPN Ethernet Segment Via,
        VF - EVPN Vlan Flood Via, AF - EVPN Vlan Aware Flood Via,
        NG - Nexthop Group Via
Source Codes:
        S - Static MPLS Route, B2 - BGP L2 EVPN,
        B3 - BGP L3 VPN, R - RSVP,
        P - Pseudowire, L - LDP,
        IP - IS-IS SR Prefix Segment, IA - IS-IS SR Adjacency Segment,
        IL - IS-IS SR Segment to LDP, LI - LDP to IS-IS SR Segment,
        BL - BGP LU, ST - SR TE Policy,
        DE - Debug LFIB
 IP 900008 [1]
            via M, 1.0.1.2, swap 900008
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930

Displaying show isis local-convergence-delay

The show isis local-convergence-delay command shows the current or last attempt at delaying the convergence of protected routes on a link down/BFD neighbor down event. If the timer aborts for some reason (such as a topology change causing a new SPF), the attempt fails.

switch#show isis local-convergence-delay 

IS-IS Instance: inst1 VRF: default
  System ID: 1111.1111.1001
  IPv4 local convergence delay configured, 5000 msecs
  IPv6 local convergence delay configured, 5000 msecs
  Level 1 attempts 0, failures 0
  Level 2 attempts 3, failures 1

  Level 2 in progress due to LINK DOWN on Vlan2138
    TI-LFA node protection is enabled for IPv4
    IPv4 Routes delayed: 0
      Delay timer started at: 2019-07-25 23:16:33
      Delay timer expires in 2 secs
    TI-LFA protection is disabled for IPv6

  Level 2 last attempt due to LINK DOWN on Vlan2138, Succeeded
    TI-LFA node protection is enabled for IPv4
    IPv4 Routes delayed: 3
      Delay timer started at: 2019-07-25 23:14:51
      Delay timer stopped at: 2019-07-25 23:14:56
    TI-LFA protection is disabled for IPv6

The detail keyword also lists all the routes that have been delayed.

switch#show isis local-convergence-delay detail
  ...
  Level 2 last attempt due to LINK DOWN on Vlan2138, Succeeded
    TI-LFA node protection is enabled for IPv4
    IPv4 Routes delayed: 3
      Delay timer started at: 2019-07-25 23:14:51
      Delay timer stopped at: 2019-07-25 23:14:56
      Delayed routes:
        10.0.7.1/32
        10.0.9.1/32
        10.0.10.1/32
    TI-LFA protection is disabled for IPv6

timers local-convergence-delay

The point of local repair (PLR) switches to the TI-LFA backup path on link failure or BFD neighbor failure but switches back to the post-convergence path once the PLR computes SPF and updates its LFIB. This sequence of events can lead to micro-loops in the topology if the PLR converges faster than other routers along the post-convergence path. So a configuration option is provided to apply a delay, after which the LFIB route being protected by the TI-LFA loop-free repair path will be replaced by the post-convergence LFIB route.

Command Mode

IS-IS address-family sub-mode

Command Syntax

timers local-convergence-delay [delay_in_seconds] protected-prefixes

Parameters
  • delay_in_seconds The convergence delay, in seconds. A default of 10 seconds is used when the command is used without an explicitly specified delay.
  • protected-prefixes The prefix which the LFIB route being protected by the TI-LFA loop-free repair path will be replaced by the post-convergence LFIB route.

Verifying IS-IS Graceful Restart (GR) Information

GR State can be one of the following:
  • Last Start/Restart was completed successfully.
  • Last Start/Restart exited after t2 (level-1/level-2) expiry.
  • Last Restart exited after t3 expiry.
  • Start/Restart in progress.
  • Graceful Restart was disabled during startup.
The following show commands are used to display the IS-IS graceful restart information.
  • The show isis graceful-restart vrf [vrf-name] command displays the GR configuration and graceful-restart related state of the IS-IS instance as well as its neighbors.
    Example
    switch#show isis graceful-restart vrf default
    IS-IS Instance: 1 VRF: default
     System ID: 0000.0000.0001
     Graceful Restart: Enabled, Graceful Restart Helper: Enabled
     State: Last Start exited after T2 (level-1) expiry
     T1 : 3s
     T2 (level-1) : 30s/20s remaining
     T2 (level-2) : 30s/not running
     T3 : not running
    
    System ID       Type   Interface     Restart Capable  Status
    is-hostname-1   L1L2   Ethernet1     Yes              Running
    is-hostname-2   L1     Ethernet2     Yes              Restarting
  • The show isis summary vrf [vrf-name] command displays the graceful restart state and helper configuration.
    Example
    switch#show isis summary vrf default
    IS-IS Instance: 1 VRF: default
     System ID: 0000.0000.0001, administratively enabled
     ....
     Graceful Restart: Enabled, Graceful Restart Helper: Enabled
  • The show isis neighbors detail vrf [vrf-name] command displays the helpers view of a restarting router.
    Example
    switch#show isis neighbors detail vrf default
    Instance  VRF      System Id  Type Interface  SNPA     State  Hold time   Circuit Id
    1         default  OT1        L1   Ethernet1  2:1:0:b  4:0:0  UP          29839   OT3.05
      Area Address(es): 49.0001
      SNPA: 2:1:0:b4:0:0
     ....
     Graceful Restart: Supported, Status: Restarting (RR rcvd, RA sent, CSNP sent)
  • The show isis interface detail vrf [vrf-name] command displays the graceful restart related stats for that interface.
    Example
    switch#show isis interface detail vrf default
    ISIS Instance: ISISQ VRF: default
      Interface Ethernet1:
        Index: 2 SNPA: P2P
        ...
        Level 1:
          Graceful Restart Status: RR sent, SA sent, RA rcvd, CSNP rcvd

IS-IS Dynamic Flooding Show Commands

Several show commands are available to monitor Dynamic Flooding. To see the flooding topology, use the show isis dynamic flooding topology command:
switch#show isis dynamic flooding topology

IS-IS Instance: Amun VRF: default
  Level 1:
    Path: ip6.00 ip4.00 ip2.00 ip1.00 ip3.00 ip5.00 ip6.00

This command displays a list of paths that describe the flooding topology. Each path is a list of nodes in the network.

To see which interfaces dynamic flooding will use, use the show isis dynamic flooding interfaces command:
switch#show isis dynamic flooding interfaces

IS-IS Instance: Amun VRF: default
  Level 1:
    Ethernet5
    Ethernet4

This shows that the system is currently flooding only on Ethernet4 and Ethernet5. Normally at least two interfaces are selected.

IS-IS Commands

Global Configuration Commands

Interface Configuration Commands

Router IS-IS Configuration Mode (Includes Address-Family Mode)

IS-IS Segment Routing Commands

Display Commands EXEC Mode

address-family

The address-family command places the switch in address-family configuration mode.

Address-family configuration mode is not a group change mode; running-config is changed immediately after commands are executed. The exit command does not affect the configuration.

The switch supports these address families:
  • ipv4-unicast
  • ipv6-unicast

The no address-family and default address-family commands delete the specified address-family from running-config by removing all commands previously configured in the corresponding address-family mode.

The exit command returns the switch to the isis configuration mode.

Command Mode

Router-IS-IS Configuration

Command Syntax

address-family [ipv4 | ipv6][MODE]

no address-family [ipv4 | ipv6][MODE]

default address-family [ipv4 | ipv6][MODE]

Parameters

  • address_family Options include:
    • ipv4 IPv4 unicast
    • ipv6 IPv6 unicast
  • MODE Options include:
    • no parameter Defaults to unicast.
    • unicast All IPv4 or IPv6 addresses are active.
Example
  • These commands enter the address family mode for IPv4 unicast.
    switch(config)#router isis Osiris
    switch(config-router-isis)#address-family ipv4 unicast 
    switch(config-router-isis-af)#
  • To exit from the IPv4 IS-IS unicast address family configuration mode, enter the following command.
    switch(config)#router isis Osiris
    switch(config-router-isis)#address-family ipv4 unicast 
    switch(config-router-isis-af)#exit
    switch(config-router-isis)#

adjacency-segment

Use the adjacency-segment command in the interface configuration mode to have the PLR computes backup paths for an adjacency segment only if the Adjacency SID sub-TLV has the B-flag (backup flag) set.

Command Mode

Interface configuration mode

Command Syntax

adjacency-segment [ipv4|ipv6] p2p [multiple][label label | indexindex] backup-eligible

no adjacency-segment [ipv4 | ipv6]p2p [multiple][label label|index index] backup-eligible

default adjacency-segment [ipv4 | ipv6]p2p multiple][label label|index index] backup-eligible

Parameters
  • ipv4 IPv4 related.
  • ipv6IPv6 related.
  • p2pP2P interface type.
  • multipleConfigure multiple Adj-SIDs.
  • label label Label value to be assigned as Adj-SID for adjacency on this interface. label range 16 -1048575.
  • index index Prefix segment identifier. index range 0-65535.
  • backup-eligibleEligible for protection.

adjacency-segment (allocation)

The adjacency-segment command allocates adjacency segments to all IS-IS adjacencies, or only those adjacencies which are to IS-IS routers that have advertised IS-IS SR capability, or to none of the adjacencies.

Command Mode

Segment-Routing MPLS Configuration

Command Syntax

adjacency-segment allocation [all-interface |none | sr-peers]

Parameters

  • allocation Allocation of Adjacency Segments.
  • all-interface Allocates adjacency segments to all IS-IS adjacencies.
  • none Disable automatic adjacency segment allocation.
  • sr-peers Allocate adjacency segments to IS-IS adjacencies with SR peers.

Example

This command allocates the adjacency segment to an sr-peer.
switch(config-router-isis-sr-mpls)#adjacency-segment allocation sr-peer

adjacency-segment (static)

The adjacency-segment command configures IS-IS adjacencies statically on the switch, so that these values are preserved even when the switch restarts. The no and the default form of the command places the switch back to the global configuration mode.

Command Mode

Interface Ethernet Configuration

Command Syntax

adjacency-segment ipv4 | ipv6 p2p [[label label-value]|[index index-value global]]

Parameters

  • ipv4 IS-IS SR adjacency segment IPv4 interface configuration.
  • ipv6 IS-IS SR adjacency segment IPv6 interface configuration.
  • label Label value to be assigned as Adj-SID for adjacency on this interface. Value ranges from 16 to 1048575.
  • index Index to be assigned as Adj-SID for adjacency on this interface. Value ranges from 0 to 65535.
  • global global adjacency SID.

Example

  • This command allocates the adjacency segment to an IPv4 p2p interface with a index value 50.
    switch(config-if-Et1)#adjacency-segment ipv4 p2p index 50 global

area leader

Use the area leader command to tune or disable the area leader election process.

Command Mode

Router configuration mode

Command Syntax

area leader [disabled | level-1 [disabled] | level-2 [disabled] | priority [num [level-1 | level-2]]]

no area leader

default area leader

Parameters
  • disabled Disables becoming the are leader.
  • level-1 Configure at Level 1.
    • disabled Disables becoming the are leader.
  • level-2 Configure at Level 2.
    • disabled Disables becoming the are leader.
  • priority Sets the area leader priority.
    • level-1 Configure at Level 1.
    • level-2 Configure at Level 2.

authentication key

Theauthentication key command configures the authentication key for the IS-IS instance causing LSPs, CSNPs and PSNPs to be authenticated.

The no authentication key and default authentication key commands disables the authentication key for the IS-IS instance.

Command Mode

ISIS-Router Configuration

Command Syntax

authentication key [0 | 7] [LAYER_VALUE]

no authentication key [0 | 7] [LAYER_VALUE]

default authentication key [0 | 7] [LAYER_VALUE]

Parameters

LAYER_VALUE layer value. Options include:
  • level-1
  • level-2

Example

These commands configure authentication for the IS-IS instance causing LSPs, CSNPs and PSNPs to be authenticated.
switch(config)#router isis 1
switch(config-router-isis)#authentication key secret
switch(config-router-isis)#

authentication mode

The authentication mode command configures authentication for the IS-IS instance causing LSPs, CSNPs and PSNPs to be authenticated.

The no authentication mode and default authentication mode commands disables authentication for the IS-IS instance.

Command Mode

ISIS-Router Configuration

Command Syntax

authentication mode [md5 | text] [LAYER_VALUE]

no authentication mode [md5 | text] [LAYER_VALUE]

default authentication mode [md5 | text] [LAYER_VALUE]

Parameters

  • LAYER_VALUE Layer value. Options include:
    • level-1
    • level-2

Example

These commands configure authentication for the IS-IS instance causing LSPs, CSNPs and PSNPs to be authenticated.
switch(config)#router isis 1
switch(config-router-isis)#authentication mode md5
switch(config-router-isis)#

bfd all-interfaces

The bfd all-interfaces command enables Bidirectional Forwarding Detection (BFD) for all IS-IS-enabled interfaces in the IPv4 or IPv6 address family.

Use the isis bfd command to configure BFD on a specific interface.

Command Mode

Router-IS-IS Address-Family Configuration

Command Syntax

bfd all-interfaces

Example

These commands enable BFD for all the interfaces on which IS-IS is enabled. By default, BFD is disabled on all the interfaces.
switch(config)#router isis 1
switch(config-router-isis)#address-family ipv4
switch(config-router-af)#bfd all-interfaces
switch(config-router-af)#

clear isis neighbor

The clear isis neighbor command clears IS-IS adjacencies that exist on an interface, or at a specific level, or the adjacencies formed with a given neighbor (either with a system ID or a hostname).

Command Mode

Privileged EXEC

Command Syntax

clear isis neighbor {Neighbor-ID | all | interface} [level-1 | level-2 | level-1-2]

Parameters

  • Neighbor-ID Clears adjacencies based on the system ID or the hostname of a neighbor.
  • all Clears all adjacencies.
  • interface Clears adjacencies for a specific interface.
  • level-1 level 1 only.
  • level-1-2 level 1-2 point-to-point only.
  • level-2 level 2 only.
Examples
  • This command clears IS-IS adjacencies with a neighbor af86.3032.1a0f.
    switch#clear isis neighbor af86.3032.1a0f
    2 neighbors cleared on instance 1
    switch#
  • This command clears all IS-IS adjacencies on an interface et1.
    switch#clear isis neighbor interface et1
    4 neighbors cleared on instance 1
    switch#
  • This command clears IS-IS adjacencies with a neighbor af86.3032.1a0f and on interface et1.
    switch#clear isis neighbor af86.3032.1a0f interface et1
    2 neighbors cleared on instance 1
    switch#
  • This command clears all IS-IS adjacencies at Level 1 and on interface et1.
    switch#clear isis neighbor interface et1 level-1
    2 neighbors cleared on instance 1
    switch#
  • This command clears Level 1-2 point-to-point adjacencies only.
    switch#clear isis neighbor all level-1-2
    0 neighbors cleared on instance 1
    switch#

fast-reroute ti-lfa mode

Use the fast-reroute ti-lfa mode to enable link or node protection for node segments and adjacency segments of a specific address-family learned on all IS-IS interfaces.

Command Mode

address-family sub-mode of the router isis mode (config-router-isis-af)

Command Syntax

fast-reroute ti-lfa mode [[[ link-protection | node-protection][level-1 | level-2]] | disabled]

Parameters
  • link-protectionProtects against the failure of the link.
  • node-protectionProtects against the failure of the neighbor mode.
  • level-1Protects prefixes only in level-1.
  • level-2Protects prefixes on in level-2.Disables the fast-reroute TI-LFA mode.

Guidelines

FRR using TI-LFA is disabled globally by default in the router IS-IS address-family sub-modes.

The interface TI-LFA configuration inherits the address-family sub-mode configuration by default.

fast-reroute ti-lfa srlg

Use the fast reroute ti-lfa srlg command to enable SRLG protection on all interfaces. This command is used in addition to configuring link-protection or node-protection. When SRLG protection is enabled, the backup paths are computed after excluding all the links that share the same SRLG with the active link that is being used by all prefix segments and adjacency segments.

Command Mode

IS-IS router address-family configuration mode

Command Syntax

fast-reroute ti-lfa srlg [strict]

Parameters

strictThe backup path is only programmed if a backup path that excludes all the SRLGs configured on the primary interface.

graceful-restart (IS-IS)

The graceful-restart command configures IS-IS graceful-restart. The command provides options to configure the t2 time or the restart-hold-time.

t2 is the maximum wait time for the LSP database to synchronize (SPF computation is not done while t2 is running). t2 can be configured for either Level-1 or Level-2 routes.

restart-hold-time is the hold time advertised by the router to its neighbors before undergoing ASU2 fast reboot.

The no graceful-restart and default graceful-restart commands disables the IS-IS graceful-restart configuration from running-config.

Command Mode

Router-IS-IS Configuration

Command Syntax

graceful-restart t2 | restart-hold-time value

no graceful-restart t2 | restart-hold-time value

default graceful-restart t2 | restart-hold-time value

Parameters

  • value The time in seconds. Value ranges from 5 to 300 seconds.
  • restart-hold-time Sets the hold time when restarting.
  • t2 Sets the LSP database sync wait time.
Examples
  • In this example an ISIS graceful restart is configured with t2 wait time of 30 seconds for Level-1 routes.
    switch(config)#router isis 1
    switch(config-router-isis)#graceful-restart t2 level-1 30
  • In this example an ISIS graceful restart is configured with restart-hold-time of 50 seconds.
    switch(config)#router isis 1
    switch(config-router-isis)#graceful-restart restart-hold-time 50

is-hostname

The is-hostname command configures the use of a human-readable string to represent the symbolic name of an IS-IS router. It also changes the output of IS-IS show commands, to show the IS-IS hostname in place of system IDs if the corresponding IS-IS hostname is known. However, syslogs still use IS-IS system IDs and not the IS-IS hostname.

By default, if a hostname is configured on the switch, it is used as the IS-IS hostname. It is also possible to unconfigure an assigned hostname for IS-IS using the no is-hostname command. When the IS-IS hostname is removed, the switch goes back to using the switchs hostname as the IS-IS hostname.

Command Mode

Router-IS-IS Configuration

Command Syntax

is-hostname string

no is-hostname

Examples
  • These commands configure the IS-IS hostname to the symbolic name ishost1 for the IS-IS router.
    switch(config)#router isis inst1
    switch(config-router-isis)#is-hostname ishost1
    switch(config-router-isis)#
  • These commands unconfigure the IS-IS hostname of the symbolic name ishost1 for the IS-IS router.
    switch(config)#router isis inst1
    switch(config-router-isis)#no is-hostname ishost1
    switch(config-router-isis)#

isis authentication key

The isis authentication key command configures the authentication key on the interface causing IS-IS Hellos to be authenticated.

The no isis authentication mode and default isis authentication mode commands disables the authentication key for the IS-IS instance.

Command Mode

Interface-Ethernet Configuration

Command Syntax

isis authentication key [0 | 7] [LAYER_VALUE]

no isis authentication key [0 | 7] [LAYER_VALUE]

default isis authentication key [0 | 7] [LAYER_VALUE]

Parameters

LAYER_VALUE Layer value. Options include:
  • level-1
  • level-2

Example

These commands configure authentication on the interface causing IS-IS Hellos to be authenticated.
switch(config)#interface Ethernet 3/6
switch(config-if-Et3/6)#isis authentication mode text
switch(config-if-Et3/6)#isis authentication key 7 cAm28+9a/xPi04o7hjd8Jw==
switch(config-if-Et3/6)#

isis authentication mode

The isis authentication mode command configures authentication on the interface causing IS-IS Hellos to be authenticated.

The no isis authentication mode and default isis authentication mode commands disables authentication for the IS-IS instance.

Command Mode

Interface-Ethernet Configuration

Command Syntax

isis authentication mode [md5 | text][LAYER_VALUE]

no isis authentication mode [md5 | text][ -[-LAYER_VALUE]-

default isis authentication mode [md5 | text][LAYER_VALUE]

Parameters

LAYER_VALUE Layer value. Options include:
  • level-1
  • level-2

Example

These commands configure authentication on the interface causing IS-IS Hellos to be authenticated.
switch(config)#interface Ethernet 3/6
switch(config-if-Et3/6)#isis authentication mode text
switch(config-if-Et3/6)#isis authentication key 7 cAm28+9a/xPi04o7hjd8Jw==
switch(config-if-Et3/6)#

isis bfd

The isis bfd command activates the corresponding IS-IS routing instance on the configuration mode interface. By default, the IS-IS routing instance is not enabled on an interface.

The no isis enable and default isis enable commands disable IS-IS on the configuration mode interface by removing the corresponding isis enable command from running-config.

Command Mode

Interface-Ethernet Configuration

Command Syntax

isis bfd

no isis bfd

default isis bfd

Example

These commands enable BFD on IS-IS interfaces.
switch(config)#interface Ethernet 5/6
switch(config-if-Et5/6)#isis bfd
switch(config-if-Et5/6)#

isis enable

The isis enable command activates the corresponding IS-IS routing instance on the configuration mode interface. By default, the IS-IS routing instance is not enabled on an interface.

The no isis enable and default isis enable commands disable IS-IS on the configuration mode interface by removing the corresponding isis enable command from running-config.

Command Mode

Interface-Ethernet Configuration

Interface-Loopback Configuration

Interface-Port-channel Configuration

Interface-VLAN Configuration

Command Syntax

isis enable instance_id

no isis enable

default isis enable

Parameters

instance_id IS-IS instance name.

Examples
  • These commands enable the IS-IS protocol on the interface ethernet 4.
    switch(config)#router isis Osiris
    switch(config-router-isis)#net 49.0001.1010.1040.1030.00
    switch(config-router-isis)#interface ethernet 4
    switch(config-if-Eth4)#isis enable Osiris
  • These commands disable the IS-IS protocol on the interface ethernet 4.
    switch(config)#interface ethernet 4
    switch(config-if-Eth4)#no isis enable

isis fast-reroute ti-lfa mode

Use the isis fast-reroute ti-lfa mode command to enable link or node protection for node segments and adjacency segments learned on a specific IS-IS interface. By default, the interface TI-LFA configuration inherits the address-family sub-mode configuration.

The no isis fast-reroute ti-lfa mode and default isis fast-reroute ti-lfa mode commands disable link or node protection for node segments and adjacency segments learned on a specific IS-IS interface.

Command Mode

Interface configuration mode.

Command Syntax

isis fast-reroute ti-lfa mode [ link-protection | node-protection | disabled ][ level-1 | level-2]

no isis fast-reroute ti-lfa mode [ link-protection | node-protection | disabled ][ level-1 | level-2 ]

default isis fast-reroute ti-lfa mode [ link-protection | node-protection | disabled ][ level-1 | level-2 ]

Parameters

  • link-protection Configures link-protection.
  • node-protection Configures node-protection.
  • disabledDisables protection over the link.
  • level-1 Optional keyword in both the router isis address-family sub-mode and interface configuration mode CLIs is used to restrict protection to node segments and adjacency segments learned through either Level-1 topologies only.
  • level-2 Optional keyword in both the router isis address-family sub-mode and interface configuration mode CLIs is used to restrict protection to node segments and adjacency segments learned through Level-2 topologies only.

isis hello-interval

The isis hello-interval command sends Hello packets from applicable interfaces to maintain the adjacency through the transmitting and receiving of Hello packets. The Hello packet interval can be modified.

The no isis hello-interval and default isis hello-interval commands restore the default hello interval of 10 seconds on the configuration mode interface by removing the isis hello-interval command from running-config.

Command Mode

Interface-Ethernet Configuration

Interface-Loopback Configuration

Interface-Port-channel Configuration

Interface-VLAN Configuration

Command Syntax

isis hello-interval time

no isis hello-interval

default isis hello-interval

Parameters

time Values range from 1 to 300; default is 10.

Examples
  • These commands configure a hello interval of 45 seconds for vlan 200.
    switch(config)#interface vlan 200
    switch(config-if-Vl200)#isis hello-interval 45
    switch(config-if-Vl200)#
  • These commands remove the configured hello interval of 45 seconds from vlan 200.
    switch(config)#interface vlan 200
    switch(config-if-Vl200)#no isis hello-interval                  
    switch(config-if-Vl200)#
  • These commands configure a hello interval of 60 seconds for interface ethernet 5.
    switch(config)#interface ethernet 5 
    switch(config-if-Et5)#isis hello-interval 60 
    switch(config-if-Et5)#
  • These commands remove the configured hello interval of 60 seconds from interface ethernet 5.
    switch(config)#interface ethernet 5 
    switch(config-if-Et5)#no isis hello-interval 
    switch(config-if-Et5)#

isis hello-multiplier

The isis hello-multiplier command specifies the number of IS-IS hello packets missed by a neighbor before the adjacency is considered down.

The no isis hello-multiplier and default isis hello-multiplier commands restore the default hello interval of 3 on the configuration mode interface by removing the isis hello-multiplier command from running-config.

Command Mode

Interface-Ethernet Configuration

Interface-Loopback Configuration

Interface-Port-channel Configuration

Interface-VLAN Configuration

Command Syntax

isis hello-multiplier factor

no isis hello-multiplier

default isis hello-multiplier

Parameters

factor Values range from 3 to 100; default is 3.

Examples
  • These commands configure a hello multiplier of 4 for vlan 200.
    switch(config)#interface vlan 200
    switch(config-if-Vl200)#isis hello-multiplier 4
    switch(config-if-Vl200)#
  • These commands remove the configured hello multiplier of 4 from vlan 200.
    switch(config)#interface vlan 200
    switch(config-if-Vl200)#no isis hello-multiplier 
    switch(config-if-Vl200)#
  • These commands configure a hello multiplier of 45 for interface ethernet 5.
    switch(config)#interface ethernet 5
    switch(config-if-Et5)#isis hello-multiplier 45
    switch(config-if-Et5)#
  • These commands remove the configured hello multiplier of 45 from interface ethernet 5.
    switch(config)#interface ethernet 5
    switch(config-if-Et5)#no isis hello-multiplier 
    switch(config-if-Et5)#

isis [ipv4|ipv6] fast-reroute ti-lfa srlg

Use the isis [ipv4|ipv6] fast-reroute ti-lfa srlg command to enable protection selectively on a specific interface. This command only enables SRLG protection for prefix segments and adjacency segments enabled on the interface.

Command Mode

Interface configuration mode

Command Syntax

isis [ipv4 | ipv6][fast-reroute ti-lfa srlg][strict | disabled]

no isis [ipv4 | ipv6][fast-reroute ti-lfa srlg][strict | disabled

default isis [ipv4 | ipv6][fast-reroute ti-lfa srlg][strict | disabled]

Parameters
  • ipv4 IS-IS IPv4 interface configuration.
  • ipv6 IS-IS IPv6 interface configuration.
  • fast-reroute Configures fast reroute.
  • ti-lfa Configures TI-LFA FRR.
  • srlg Excludes same SRLG links from backup path.
  • strict The backup path is only programmed only if a backup path that excludes all the SRLGs configured on the primary interface. If strict is not provided and an SRLG excluding path is not available, TI-LFA programs the backup path that excluded the maximum number of SRLGs possible.
  • disabled Use to selectively disable SRLG protection on an interface. This is useful when SRLG protection is enabled globally for all interfaces but needs to be selectively disabled for a specific interface.

isis ipv6 metric

The isis ipv6 metric command configures the IPv6 metric.

The no isis ipv6 metric and default isis ipv6 metric commands restore the default metric of 10 on the configuration mode interface.

Command Mode

Interface-Ethernet Configuration

Command Syntax

isis ipv6 metric metric_value

no isis ipv6 metric

default isis ipv6 metric

Parameters

metric_value Values range from 1 to 16777214; default is 10.

Example

These commands configure the IPv6 metric.
switch(config)#interface Ethernet 5/6
switch(config-if-Et5/6)#isis ipv6 metric 30
switch(config-if-Et5/6)#

isis lsp tx interval

The isis lsp tx interval command sets the interval at which IS-IS sends link-state information on the interface.

The no isis lsp tx interval and default isis lsp tx interval commands restores the default setting of 33 ms. by removing the isis lsp tx interval command from running-config.

Command Mode

Interface-Ethernet Configuration

Interface-Loopback Configuration

Interface-Port-channel Configuration

Interface-VLAN Configuration

Command Syntax

isis lsp tx interval period

no isis lsp tx interval

default isis lsp tx interval

Parameters

period Value ranges from 1 through 3000. Default interval is 33 ms.

Examples
  • This command sets the LSP interval on interface interface ethernet 5 to 600 milliseconds.
    switch(config)#interface ethernet 5
    switch(config-if-Et5)#isis lsp tx interval 600
    switch(config-if-Et5)#
  • This command removes the LSP interval on interface ethernet 5.
    switch(config)#interface ethernet 5
    switch(config-if-Et5)#no isis lsp tx interval
    switch(config-if-Et5)#

isis metric

The isis metric command sets cost for sending information over an interface.

The no isis metric and default isis metric commands restore the metric to its default value of 10 by removing the isis metric command from running-config.

Command Mode

Interface-Ethernet Configuration

Interface-Loopback Configuration

Interface-Port-channel Configuration

Interface-VLAN Configuration

Command Syntax

isis metric metric_cost

no isis metric

default isis metric

Parameters

metric_cost Values range from 1 to 1677214. Default value is 10.

Examples
  • These commands configure a metric cost of 30 for sending information over interface ethernet 5.
    switch(config)#router isis Osiris
    switch(config-router-isis)#interface ethernet 5
    switch(config-if-Et5)#isis metric 30
    switch(config-if-Et5)#
  • These commands remove the configured metric cost of 30 from interface ethernet 5.
    switch(config)#router isis Osiris
    switch(config-router-isis)#interface ethernet 5
    switch(config-if-Et5)#no isis metric
    switch(config-if-Et5)#

isis multi-topology

The isis multi-topology command configures the IPv4 or IPv6 address family individually on an interface with both IPv4 and IPv6 addresses.

The no isis multi-topology and default isis multi-topologycommands restores the default interface to both IPv4 and IPv6 address families.

Command Mode

Interface-Ethernet Configuration

Command Syntax

isis multi-topology address-family ipv4 unicast

no isis multi-topology address-familyipv4unicast

default isis multi-topology address-familyipv4unicast

Examples
  • These commands configure the IPv4 address family on an interface with both IPv4 and IPv6 addresses.
    switch(config)#interface Ethernet 5/6
    switch(config-if-Et5/6)#isis multi-topology address-family ipv4 unicast
    switch(config-if-Et5/6)#
  • These commands configure the IPv6 address family on an interface with both IPv4 and IPv6 addresses.
    switch(config)#interface Ethernet 5/6
    switch(config-if-Et5/6)#isis multi-topology address-family ipv6 unicast
    switch(config-if-Et5/6)#
  • These commands configure both the IPv4 and IPv6 address families on an interface.
    switch(config)#interface Ethernet 5/6
    switch(config-if-Et5/6)#no isis multi-topology address-family unicast
    switch(config-if-Et5/6)#

isis network

The isis network command sets the configuration mode interface as a point-to-point link. By default, interfaces are configured as broadcast links.

The no isis network and default isis network commands set the configuration mode interface as a broadcast link by removing the corresponding isis network command from running-config.

Command Mode

Interface-Ethernet Configuration

Interface-Loopback Configuration

Interface-Port-Channel Configuration

Interface-VLAN Configuration

Command Syntax

isis network point-to-point

no isis network

default isis network

Examples
  • These commands configure interface ethernet 10 as a point-to-point link.
    switch(config)#interface ethernet 10
    switch(config-if-Etl0)#isis network point-to-point
    switch(config-if-Etl0)#
  • This command restores interface ethernet 10 as a broadcast link.
    switch(config-if-Etl0)#no isis network
    switch(config-if-Etl0)#

isis passive

The isis passive command configures the configuration-mode interface as passive. The switch will continue to advertise the IP address in the LSP, but the interface will not send or receive IS-IS control packets.

The no isis passive command removes the passive configuration, allowing the interface to send and receive IS-IS control packets. The default isis passive command sets the interface to the default interface activity setting by removing the corresponding isis passive or no isis passive statement from running-config.

Command Mode

Interface-Ethernet Configuration

Interface-Loopback Configuration

Interface-Port-Channel Configuration

Interface-VLAN Configuration

Command Syntax

isis passive

no isis passive

default isis passive

Examples
  • These commands configure Ethernet interface 10 as a passive interface.
    switch(config)#interface ethernet 10
    switch(config-if-Etl0)#isis passive
    switch(config-if-Etl0)#
  • These commands restore Ethernet interface 10 as an active interface.
    switch(config)#interface ethernet 10
    switch(config-if-Etl0)#no isis passive
    switch(config-if-Etl0)#

isis priority

The isis priority command sets the IS-IS priority for the interface.

The default priority is 64. The network device with the highest priority will be elected as the designated intermediate router to send link-state advertisements for that network.

The no isis priority and default isis priority commands restore the default priority (64) on the configuration mode interface.

Command Mode

Interface-Ethernet Configuration

Interface-Loopback Configuration

Interface-Port-channel Configuration

Interface-VLAN Configuration

Command Syntax

isis priority priority_level

no isis priority

default isis priority

Parameters

priority_level Value ranges from 0 to 127. Default value is 64.

Examples
  • These commands configure a IS-IS priority of 60 on interface ethernet 5.
    switch(config)#router isis Osiris
    switch(config-router-isis)#interface ethernet 5
    switch(config-if-Et5)#isis priority 60
    switch(config-if-Et5)#
  • These commands restores the default IS-IS priority of 64 from interface ethernet 5.
    switch(config)#router isis Osiris
    switch(config-router-isis)#interface ethernet 5
    switch(config-if-Et5)#no isis priority 
    switch(config-if-Et5)#
  • These commands configure the switch with a priority of 64 for interface vlan 7.
    switch(config)#interface vlan 7
    switch(config-if-Vl7)#isis priority 64
    switch(config-if-Vl7)#
  • These command restores the default IS-IS priority of 64 for 64.
    switch(config)#interface vlan 7
    switch(config-if-Vl7)#no isis priority
    switch(config-if-Vl7)#

is-type

The is-type command configures the routing level for an IS-IS instance.

An IS-IS router can be configured as Level-1-2 which can form adjacencies and exchange routing information with both Level-1 and Level-2 routers. A Level-1-2 router can be configured to transfer routing information from Level-1 to Level-2 areas and vice versa (via route leaking). By default, all routes from Level-1 area are always leaked into Level-2 network.

Command Mode

Router-IS-IS Configuration

Command Syntax

is-type LAYER_VALUE

Parameters

  • LAYER_VALUE Layer value options include:
    • level-1
    • level-1-2
    • level-2
Examples
  • These commands configure Level 1-2 routing.
    switch(config)#router isis Osiris
    switch(config-router-isis)#is-type level-1-2
    switch(config-router-isis)#
  • These commands configure Level 2 routing.
    switch(config)#router isis Osiris
    switch(config-router-isis)#is-type level-2
    switch(config-router-isis)#

log-adjacency-changes (IS-IS)

The log-adjacency-changes command sets the switch to send Syslog messages when it detects link state changes or when it detects that a neighbor state has changed.

The default option is active when running-config does not contain any form of the command. Entering the command in any form replaces the previous command state in running-config.

Command Mode

Router-IS-IS Configuration

Command Syntax

log-adjacency-changes

no log-adjacency-changes

default log-adjacency-changes

Examples
  • These commands configure the switch to send a Syslog message when a neighbor state changes.
    switch(config)#router isis Osiris
    switch(config-router-isis)#log-adjacency-changes
    switch(config-router-isis)#
  • These commands configure not to log the peer changes.
    switch(config)#router isis Osiris
    switch(config-router-isis)#no log-adjacency-changes
    switch(config-router-isis)#

lsp dynamic flooding

Use the lsp flooding dynamic command to configure dynamic flooding. Dynamic flooding must be enabled on all roters in the area. The no form of the command removes LSP dynamic flooding. LSP flooding dynamic is disabled by default.

Command Mode

Router configuration mode

Command Syntax

lsp flood dynamic [level-1 | level-2]

no lsp flood dynamic [level-1 | level-2]

default lsp flood dynamic [level-1 | level-2]

Parameters
  • level-1 Level 1 adjeacencies.
  • level-2 Level 2 adjencencies.
Example
switch(config)#router isis Amun
switch(config-router-isis)#net 49.0000.0000.3333.00
switch(config-router-isis)#is-hostname ip3
switch(config-router-isis)#lsp flooding dynamic

match isis level

The match isis level command configures a route map to match on ISIS level. It filters the Level-1 or Level-2 routes by using route maps match statement.

The no match isis level and default match isis level commands disables the match ISIS level configuration from running-config.

Command Mode

Route-map Configuration

Command Syntax

match isis level [level-1 | level-2]

no match isis level [level-1 | level-2]

default match isis level [level-1 | level-2]

Parameters

  • level-1 IS-IS level 1.
  • level-2 IS-IS level 2.

Example

These commands place the switch in route-map mode, and configures a route map to match isis level to Level-1.
switch(config)#route-map Test
switch(config-route-map-test)#match isis level level-1

mpls label range

The mpls label range command derives the indices of the actual MPLS label on the SRGB advertised by the router. The default value of SRGB in EOS is Base: 900000, Size: 65536. In other words, the labels that any global segment could represent is between 900000-965535.

Command Mode

Global Configuration

Command Syntax

mpls label range value

Parameters

value Specifies the Segment Routing global range.
  • dynamic Specifies labels reserved for dynamic assignment. Default value is (100000) (262144).
    • IS-IS-sr Specifies labels reserved for IS-IS SR global segment identifiers (SIDs). Default value is (900000) (65536).
    • static Specifies labels reserved for static MPLS routes. Default value is (16) (99984).

Example

The following command configures an IS-IS SR global range with a value of (900000)-- starting label range, (65536)--Numbers of labels to reserve.
switch(config)#mpls label range isis-sr 900000 65536

multi-topology

The multi-topology command configures IS-IS Multi-Topology (MT) support (disabled by default), enabling an IS-IS router to compute a separate topology for IPv4 and IPv6 links in the network. With MT configured, not all the links in a network need to support both IPv4 and IPv6. Some can support IPv4 or IPv6 individually. The IPv4 SPF will install IPv4 routes using the IPv4 topology, and similarly the IPv6 SPF will install IPv6 routes using the IPv6 topology. Without MT support, all links in an IS-IS network need to support the same set of address families. When MT is enabled, and each link has a separate IPv4 metric and IPv6 metric.

The no multi-topology and default multi-topology commands restores the default interface to both IPv4 and IPv6 address families.

Command Mode

Router IS-IS Address-Family Configuration

Command Syntax

multi-topology

no multi-topology

default multi-topology

Examples
  • These commands configure MT for the IS-IS router.
    switch(config)#router isis 1
    switch(config-router-isis)#address-family ipv6 unicast
    switch(config-router-isis-af)#multi-topology
    switch(config-router-isis-af)#
  • These commands unconfigure MT for the IS-IS router.
    switch(config)#router isis 1
    switch(config-router-isis)#address-family ipv6 unicast
    switch(config-router-isis-af)#no multi-topology
    switch(config-router-isis-af)#

net

The net command configures the Network Entity Title of the IS-IS instance. By default, no NET is defined.

The no net and default net commands removes the NET from running-config.

Command Mode

Router-IS-IS Configuration

Command Syntax

net mask_hex

no net

default net

Parameters

  • maxk_hex Mask value. Format is hh.hhhh.hhhh.hhhh.hhhh.hhhh.hhhh.hhhh.hhhh.hhhh.00.
Examples
  • These commands specify the NET as 49.0001.1010.1040.1030.00, in which the system ID is 1010.1040.1030, area ID is 49.0001.
    switch(config)#router isis Osiris
    switch(config-router-isis)#net 49.0001.1010.1040.1030.00
    switch(config-router-isis)#
  • These commands remove NET 49.0001.1010.1040.1030.00 from running-config.
    switch(config)#router isis Osiris
    switch(config-router-isis)#no net 49.0001.1010.1040.1030.00
    switch(config-router-isis)#

node-segment

The node-segment command associates the node segments with prefix mask length /32 (IPV4) or /128 (IPV6) addresses. The node-segment command must be issued on an IS-IS-enabled loop back interface.

Command Mode

Loop-back Interface Configuration

Command Syntax

node-segment [ipv4 | ipv6] index value

Parameters

  • ipv4 Specifies the IPv4 node configuration.
  • ipv6 Specifies the IPv6 node configuration.
  • index Node segment identifier.
  • value Index to be mapped with IP prefix. Value ranges from 0-65535.
Examples
  • The following commands are used to associate a node-segment with an IPv4 address.
    switch(config)#int loopback 1
    switch(config-if-Lo1)#ip address 21.1.1.1/32
    switch(config-if-Lo1)#node-segment ipv4 index 5
  • The following commands are used to associate a node-segment with an IPv6 address.
    switch(config)#int loopback 1
    switch(config-if-Lo1)#ipv6 add 2000::24/128
    switch(config-if-Lo1)#node-segment ipv6 index 5
  • The following example shows a warning thrown at the CLI when a /32 or /128 address is not configured on the interface.
    switch(config)#int loopback 1
    switch(config-if-Lo1)#ip address 21.1.1.1/24
    switch(config-if-Lo1)#node-segment ipv4 index 1
    ! /32 IPv4 address is not configured on the interface
  • The following command removes the node-segment from IS-IS SR from an interface.
    switch(config-if-Lo1)#no node-segment ipv4 index 1

passive (IS-IS)

The passive command configures the specified IS-IS interface as passive. The switch will continue to advertise the IP address in the LSP, but the interface will not send or receive IS-IS control packets.s

The no passive command removes the passive configuration, allowing the interface to send and receive IS-IS control packets. The default passive command sets the interface to the default interface activity setting by removing the corresponding passive or no passive statement from running-config.

Command Mode

Router-IS-IS Configuration

Command Syntax

passive INTERFACE_NAME

no passive INTERFACE_NAME

default passive INTERFACE_NAME

Parameters

INTERFACE_NAME Options include:
  • ethernet e_range Ethernet interface list.
  • loopback l_range loopback interface list.
  • port-channel p_range channel group interface list.
  • vlan v_range VLAN interface list.

Valid e_range, l_range, p_range, and v_range formats include number, range, or comma-delimited list of numbers and ranges.

Examples
  • These commands configure Ethernet interface 10 as a passive interface.
    switch(config)#router isis Osiris
    switch(config-router-isis)#passive ethernet 10
    switch(config-router-isis)#
  • These commands restore Ethernet interface 10 as an active IS-IS interface.
    switch(config)#router isis Osiris
    switch(config-router-isis)#no passive ethernet 10
    switch(config-router-isis)#

prefix-segment

The prefix-segment command associates prefix segments with any IS-IS prefix a router is originating an IP Reachability TLV for.

Command Mode

Segment-Routing MPLS Configuration

Command Syntax

prefix-segment ip-address index value

Parameters

  • ip-address It can be IP address, or IP address with prefix, or an IPv6 address prefix.
  • index Node segment identifier.
  • value Index to be mapped with IP prefix. Value ranges from 0-65535.

Example

The following commands are used to associate a prefix segment with an IPv4 address with index value of 50.
switch(config)#router isis instance1
switch(config-router-isis)#segment-routing mpls
switch(config-router-isis-sr-mpls)#prefix-segment 1.1.1.0/24 index 50

proxy-node-segment

The proxy-node-segment command configures a proxy-node-SID for a IS-IS prefix originating from the router that does not support IS-IS SR.

Command Mode

Segment-Routing MPLS Configuration

Command Syntax

proxy-node-segment ip-address index value

Parameters
  • ip-address It can be IP address, or IP address with prefix, or an IPv6 address prefix.
  • index Node segment identifier.
  • value Index to be mapped with IP prefix. Value ranges from 0-65535.

Example

A proxy-node-segment associates a /32 or a /128 route with an SID as shown below.
switch(config)#router isis instance1
switch(config-router-isis)#segment-routing mpls
switch(config-router-isis-sr-mpls)#proxy-node-segment 1.1.1.0/32 index 50

redistribute (IS-IS)

The redistribute command redistributes the specified types of routes into IS-IS.

The no redistribute and default redistribute commands disable route redistribution from the specified domain by removing the corresponding redistribute statement from running-config.

Command Mode

Router-IS-IS Configuration

Command Syntax

redistribute ROUTE_TYPE

no redistribute ROUTE_TYPE

default redistribute ROUTE_TYPE

Parameters

ROUTE_TYPE The route type for which routes are redistributed. These are the option to include.
  • bgpredistribute BGP routes
  • connectedredistribute connected routes
  • ospfredistribute OSPF routes
  • ospfv3redistribute OSPFv3 routes
  • staticredistribute static routes
Examples
  • These commands redistribute connected routes into the IS-IS domain.
    switch(config)#router isis Test
    switch(config-router-isis)#redistribute connected
  • These commands redistribute static routes into the IS-IS domain.
    switch(config)#router isis Test
    switch(config-router-isis)#redistribute static
  • These commands redistribute the BGP routes into ISIS domain in the address-family mode.
    Switch(config)#router isis 1
    Switch(config-router-isis)#address-family ipv4
    Switch(config-router-isis-af)#redistribute bgp route-map bgp-to-isis-v4
  • These commands redistribute the BGP routes into ISIS domain in the router-isis mode.
    Switch(config)#router isis 1
    Switch(config-router-isis)#redistribute bgp route-map bgp-to-isis

redistribute bgp route-map

The redistribute bgp route-map command redistributes the BGP routes from the specified route map into IS-IS. Only one route map can be specified; reissuing the command overrides any previous configuration.

The no redistribute bgp and default redistribute bgpcommands disable BGP route redistribution from the specified domain by removing the redistribute bgp statement from running-config.

The command is available in both router isis configuration mode and the address-family submode. The command is rejected if configured in both modes at the same time. Issuing the no or default command in router isis configuration mode has no effect on redistribution configured in the address-family submode.

Note: If the command is configured in an address-family submode, it only redistributes routes from that address family. If it is configured in router-isis mode, it applies to all enabled address families.

Command Mode

Router-IS-IS Configuration

Router-IS-IS Address-Family Configuration

Command Syntax

redistribute bgp route-map map_name

no redistribute bgp

default redistribute ROUTE_TYPE

Parameters

map_name Route map to be used for redistribution of BGP routes.

Examples
  • These commands redistribute IPv4 BGP routes from the route map called bgp-to-isis-v4 into the ISIS domain.
    switch(config)#router isis 1
    switch(config-router-isis)#address-family ipv4
    switch(config-router-isis-af)#redistribute bgp route-map bgp-to-isis-v4
    switch(config-router-isis-af)#
  • These commands redistribute all BGP routes from the route map bgp-to-isis into ISIS.
    switch(config)#router isis 1
    switch(config-router-isis)#redistribute bgp route-map bgp-to-isis

router isis

The router isis command places the switch in router ISIS configuration mode.

Router ISIS configuration mode is not a group change mode; running-config is changed immediately after commands are executed. The exit command does not affect the configuration.

The no router isis command deletes the IS-IS instance.

The exit command returns the switch to global configuration mode.

Command Mode

Global Configuration

Command Syntax

router isis instance_name [VRF_INSTANCE]

no router isis instance_name

default router isis instance_name

Parameters

  • instance_name routing instance.
  • VRF_INSTANCE
    • no parameter
    • vrf vrf_name
Examples
  • These commands places the switch in the router isis mode and creates an IS-IS routing instance named Osiris.
    switch(config)#router isis Osiris
    switch(config-router-isis)#
  • This command attempts to open an instance with a different routing instance name from that of the existing instance. The switch displays an error and stays in global configuration mode.
    switch(config)#router isis Osiris
    % More than 1 ISIS instance is not supported
    switch(config)#
  • This command deletes the IS-IS instance.
    switch(config)#no router isis Osiris
    switch(config)#

show ip route

When services like LDP pseudowires, BGP LU, L2 EVPN, or L3 MPLS VPN use IS-IS SR tunnels as an underlay, these services are automatically protected by TI-LFA tunnels that protect the IS-IS SR tunnels. The show ip route command displays the hierarchy of the overlay-underlay-TI-LFA tunnels.

 B        2001:db8:3::/48 [200/0]                                                                     
           via 2002::b00:301/128, IS-IS SR tunnel index 3, label 122697                               
              via TI-LFA tunnel index 5, label imp-null(3)                                            
                 via fe80::200:76ff:fe03:0, Ethernet26/1, label imp-null(3)                           
                 backup via fe80::200:76ff:fe01:0, Ethernet30/1, label 900002 900003

segment-routing mpls

The segment-routing mpls command places the switch in the segment-routing mpls configuration mode.

The no segment-routing mpls and default segment-routing mpls commands disable IS-IS SR and delete all IS-IS SR configurations.

Command Mode

Router IS-IS Configuration

Command Syntax

segment-routing mpls

no segment-routing mpls

default segment-routing mpls

Example

The following commands place the switch in segment-routing mpls configuration mode.
switch(config)#router isis instance1
switch(config-router-isis)#segment-routing mpls
switch(config-router-isis-sr-mpls)#

set isis level

The set isis level command configures a route map to set ISIS level.

The no set isis level and default set isis level commands disables the set ISIS level configuration from running-config.

Command Mode

Route-map Configuration

Command Syntax

set isis level [level-1 | level-2 | level-1-2]

no set isis level[level-1 | level-2 | level-1-2]

default set isis level[level-1 | level-2 | level-1-2]

Parameters
  • level-1 IS-IS level 1.
  • level-2 IS-IS level 2.
  • level-1-2 IS-IS level 1 and level 2.

Example

These commands place the switch in the route-map mode, and configures a route map to set isis level to level-1.
switch(config)#route-map Test
switch(config-route-map-test)#set isis level level-1

set-overload-bit

The set-overload-bit command used without the on-startup option will inform other devices not to use this switch in SPF computation. When used with the on-startup parameter, the overload bit is set for the interval after startup.

The no set-overload-bit and default set-overload-bit commands removes the corresponding set-overload-bit command from running-config.

Command Mode

Router-IS-IS Configuration

Command Syntax

set-overload-bit TIMING

no set-overload-bit

default set-overload-bit

Parameters

TIMING Options include:
  • no parameter
  • on-startup 1 to 3600
Examples
  • These commands configure the switch to sets the overload bit to 120 seconds after startup.
    switch(config)#router isis Osiris
    switch(config-router-isis)#set-overload-bit on-startup 120
    switch(config-router-isis)#
  • These commands remove the configured overload bit of 120 seconds from the running-config.
    switch(config)#router isis Osiris
    switch(config-router-isis)#no set-overload-bit on-startup 
    switch(config-router-isis)#

show isis database detail

Theshow isis database detail command displays a view of LSPDB of different devices in the IS-IS domain.

Command Mode

EXEC

Command Syntax

show isis database detail

Example

The command output displays the TLVs and sub-TLVs that are being self-originated or the ones that have been received from other routers.
switch#show isis database detail

ISIS Instance: inst1 VRF: default
 ISIS Level 2 Link State Database
 LSPID Seq Num Cksum Life IS Flags
 1111.1111.1001.00-00 10 63306 751 L2 <>
 NLPID: 0xCC(IPv4) 0x8E(IPv6)
 Area address: 49.0001
 Interface address: 1.0.7.1
 Interface address: 1.0.0.1
 Interface address: 2000:0:0:47::1
 Interface address: 2000:0:0:40::1
 IS Neighbor : lf319.53 Metric: 10
    LAN-Adj-sid: 100000 flags: [ L V ] weight: 0 system ID: 1111.1111.1002
 IS Neighbor (MT-IPv6): lf319.53 Metric: 10
    LAN-Adj-sid: 100001 flags: [ L V F ] weight: 0 system ID: 1111.1111.1002
 Reachability : 1.0.11.0/24 Metric: 1 Type: 1 Up
    SR Prefix-SID: 10 Flags: [ R ] Algorithm: 0
 Reachability : 1.0.3.0/24 Metric: 1 Type: 1 Up
 Reachability : 1.0.7.1/32 Metric: 10 Type: 1 Up
    SR Prefix-SID: 2 Flags: [ N ] Algorithm: 0
 Reachability : 1.0.0.0/24 Metric: 10 Type: 1 Up
 Reachability (MT-IPv6): 2000:0:0:4b::/64 Metric: 1 Type: 1 Up
    SR Prefix-SID: 11 Flags: [ R ] Algorithm: 0
 Reachability (MT-IPv6): 2000:0:0:43::/64 Metric: 1 Type: 1 Up
 Reachability (MT-IPv6): 2000:0:0:47::1/128 Metric: 10 Type: 1 Up
    SR Prefix-SID: 3 Flags: [ N ] Algorithm: 0
 Reachability (MT-IPv6): 2000:0:0:40::/64 Metric: 10 Type: 1 Up
 Router Capabilities: 252.252.1.252 Flags: [ ]
    SR Capability: Flags: [ I V ]
       SRGB Base: 900000 Range: 65536
 Segment Binding: Flags: [ F ] Weight: 0 Range: 1 Pfx 2000:0:0:4f::1/128
    SR Prefix-SID: 19 Flags: [ ] Algorithm: 0
 Segment Binding: Flags: [ ] Weight: 0 Range: 1 Pfx 1.0.15.1/32
    SR Prefix-SID: 18 Flags: [ ] Algorithm: 0

show isis database

The show isis database command displays the link state database of IS-IS. The default command displays active routes and learned routes.

Command Mode

EXEC

Command Syntax

show isis database [INSTANCES][INFO_LEVEL]

show isis database [INFO_LEVEL] [VRF_INSTANCE]

Parameters

  • INSTANCES Options include:
    • no parameter
    • instance_name
  • INFO_LEVEL Options include:
    • no parameter
    • detail
  • VRF_INSTANCE Specifies the VRF instance.
    • no parameter
    • vrf vrf_name
Display Values
  • ISIS Instance
  • LSPID
  • Seq Num
  • Cksum
  • Life
  • IS
Examples
  • This command displays general information about the link state database of IS-IS.
    switch#show isis database
    
    ISIS Instance: Osiris
      ISIS Level 2 Link State Database
        LSPID                 Seq Num   Cksum  Life  IS Flags
        1212.1212.1212.00-00  4         714    1064  L2 <>
        1212.1212.1212.0a-00  1         57417  1064  L2 <>
        2222.2222.2222.00-00  6         15323  1116  L2 <>
        2727.2727.2727.00-00  10        15596  1050  L2 <>
        3030.3030.3030.00-00  12        62023  1104  L2 <>
        3030.3030.3030.c7-00  4         53510  1104  L2 <>
    switch>
  • This command displays detailed information about the link state database of IS-IS.
    switch#show isis database detail
    
    ISIS Instance: Osiris
      ISIS Level 2 Link State Database
        LSPID                 Seq Num   Cksum  Life  IS Flags
        1212.1212.1212.00-00  4         714    1060  L2 <>
          Area address: 49.0001
          Interface address: 10.1.1.2
          Interface address: 2002::2
          IS Neighbor:   1212.1212.1212.0a Metric: 10
          Reachability: 10.1.1.0/24 Metric: 10 Type: 1
          Reachability: 2002::/64 Metric: 10 Type: 1
        1212.1212.1212.0a-00  1         57417  1060  L2 <>
          IS Neighbor:   2727.2727.2727.00 Metric: 0
          IS Neighbor:   2222.2222.2222.00 Metric: 0
          IS Neighbor:   1212.1212.1212.00 Metric: 0
        2222.2222.2222.00-00  6         15323  1112  L2 <>
          Area address: 49.0001
          Interface address: 10.1.1.1
          Interface address: 10.1.1.3
          Interface address: 2002::3
          IS Neighbor:   1212.1212.1212.0a Metric: 10
          Reachability: 10.1.1.0/24 Metric: 10 Type: 1
          Reachability: 10.1.1.0/24 Metric: 10 Type: 1
          Reachability: 2002::/64 Metric: 10 Type: 1
        2727.2727.2727.00-00  10        15596  1046  L2 <>
          Area address: 49.0001
          Interface address: 10.1.1.1
          Interface address: 30.1.1.1
          Interface address: 2002::1
          Interface address: 2001::1
          IS Neighbor:   1212.1212.1212.0a Metric: 10
          IS Neighbor:   3030.3030.3030.c7 Metric: 10
          Reachability: 10.1.1.0/24 Metric: 10 Type: 1
          Reachability: 30.1.1.0/24 Metric: 10 Type: 1
          Reachability: 2002::/64 Metric: 10 Type: 1
          Reachability: 2001::/64 Metric: 10 Type: 1
        3030.3030.3030.00-00  12        62023  1100  L2 <>
          Area address: 49.0001
          Interface address: 30.1.1.2
          Interface address: 2001::2
          IS Neighbor:   3030.3030.3030.c7 Metric: 10
          Reachability: 12.1.1.0/24 Metric: 1 Type: 1
          Reachability: 110.1.1.0/24 Metric: 0 Type: 1
          Reachability: 30.1.1.0/24 Metric: 10 Type: 1
          Reachability: 2001::/64 Metric: 10 Type: 1
        3030.3030.3030.c7-00  4         53510  1100  L2 <>
          IS Neighbor:   2727.2727.2727.00 Metric: 0
          IS Neighbor:   3030.3030.3030.00 Metric: 0
    switch>

show isis dynamic flooding

Use the show isis dynamic flooding command to monitor Dynamic Flooding.

Command Mode

EXEC

Command Syntax

show isis dynamic flooding [interfaces | level-1 | level-2 | nodes | paths | topology | interface]

Parameters
  • interfaces Flooding interfaces
  • level-1 Level 1 adjencencies only.
  • level-2 Level 2 adjencencies only.
  • nodesNodes in the flooding topology.
  • pathsPaths in the flooding topology.
  • topologyFlooding topology.
Examples
  • The command show isis dynamic flooding nodes shows the list of nodes in the area and the indices for the nodes.
    switch#show isis dynamic flooding nodes
    IS-IS Instance: Amun VRF: default
       Level 1 Nodes:
         Index           Node ID
         0               ip6.00
         1               ip4.00
         2               ip2.00
         3               ip1.00
         4               ip3.00
         5               ip5.00
  • The command show isis dynamic flooding paths shows the list of paths in the flooding topology using node indices.
    switch#show isis dynamic flooding paths
    IS-IS Instance: Amun VRF: default
      Level 1:
        Path: 0 1 2 3 4 5 0
  • To view the flooding topology, use the show isis dynamic flooding topology command:
    switch#show isis dynamic flooding topology
    IS-IS Instance: Amun VRF: default
      Level 1:
        Path: ip6.00 ip4.00 ip2.00 ip1.00 ip3.00 ip5.00 ip6.00
  • To view which interfaces dynamic flooding will use, use the show isis dynamic flooding interfaces command:
    switch#show isis dynamic flooding interfaces
    IS-IS Instance: Amun VRF: default
      Level 1:
        Ethernet5
        Ethernet4

show isis graceful-restart vrf

The show isis graceful-restart vrf command displays the GR configuration and graceful-restart related state of the IS-IS instance as well as its neighbors.

Command Mode

EXEC

Command Syntax

show isis graceful-restart vrf vrf-name

Example

In this example the show isis graceful-restart command displays the output for the default vrf instance.
switch#show isis graceful-restart vrf default
IS-IS Instance: 1 VRF: default
 System ID: 0000.0000.0001
 Graceful Restart: Enabled, Graceful Restart Helper: Enabled
 State: Last Start exited after T2 (level-1) expiry
 T1 : 3s
 T2 (level-1) : 30s/20s remaining
 T2 (level-2) : 30s/not running
 T3 : not running

System ID       Type   Interface     Restart Capable  Status
is-hostname-1   L1L2   Ethernet1     Yes              Running
is-hostname-2   L1     Ethernet2     Yes              Restarting

show isis hostname

The show isis hostname command displays mapping between the System ID and IS-IS hostname.

Command Mode

EXEC

Command Syntax

show isis hostname

Example

This command mapping between the System ID and IS-IS hostnames host1 and host2.
switch#show isis hostname
ISIS Instance: 1 VRF: default
Level System ID Hostname
L1 1111.1111.1001 host1
L1 1111.1111.1002 host2

show isis interface

The show isis interface command displays interface information for the IS-IS instance.

Command Mode

EXEC

Command Syntax

show isis interface [INSTANCES][INTERFACE_NAME][INFO_LEVEL]

show isis interface [INTERFACE_NAME] [INFO_LEVEL][VRF_INSTANCE]

Parameters
  • INSTANCES Options include:
    • no parameter
    • instance_name
  • INTERFACE_NAME Values include:
    • no parameter all interfaces.
    • ethernet e_num Ethernet interface specified by e_num.
    • loopback l_num Loopback interface specified by l_num.
    • management m_num Management interface specified by m_num.
    • port-channel p_num Port channel interface specified by p_num.
    • vlan v_num VLAN interface specified by v_num.
    • vxlan vx_num VXLAN interface specified by vx_num.
  • INFO_LEVEL Options include:
    • no parameter
    • detail
  • VRF_INSTANCE specifies the VRF instance.
    • no parameter
    • vrf vrf_name
Display Values
  • ISIS Instance
  • System ID
  • Index
  • MTU
  • Metric
  • LAN-ID
  • DIS
  • Type
  • Interface
  • SNPA
  • State
  • Hold time
Examples
  • This command displays general IS-IS information for instance Osiris.
    switch#show isis interface
    
    ISIS Instance: Osiris
      Interface Vlan20:
        Index: 59 SNPA: 0:1c:73:c:5:7f
        MTU: 1497 Type: broadcast
        Level 2:
          Metric: 10, Number of adjacencies: 2
          LAN-ID: 1212.1212.1212, Priority: 64
          DIS: 1212.1212.1212, DIS Priority: 64
      Interface Ethernet30:
        Index: 36 SNPA: 0:1c:73:c:5:7f
        MTU: 1497 Type: broadcast
        Level 2:
          Metric: 10, Number of adjacencies: 1
          LAN-ID: 3030.3030.3030, Priority: 64
          DIS: 3030.3030.3030, DIS Priority: 64
  • This command displays detailed IS-IS information for instance Osiris.
    switch#show isis interface detail
    
    ISIS Instance: Osiris
      Interface Vlan20:
        Index: 59 SNPA: 0:1c:73:c:5:7f
        MTU: 1497 Type: broadcast
        Level 2:
          Metric: 10, Number of adjacencies: 2
          LAN-ID: 1212.1212.1212, Priority: 64
          DIS: 1212.1212.1212, DIS Priority: 64
        Adjacency 2222.2222.2222:
          State: UP, Level: 2 Type: Level 2 IS
          Hold Time: 30, Supported Protocols: ipv4, ipv6
          SNPA: 2:1:0:c:0:0, Priority: 64
          IPv4 Interface Address: 10.1.1.3
          IPv6 Interface Address: fe80::1:ff:fe0c:0
          Areas:
            49.0001
        Adjacency 1212.1212.1212:
          State: UP, Level: 2 Type: Level 2 IS
          Hold Time: 9, Supported Protocols: ipv4, ipv6
          SNPA: 2:1:0:d:0:0, Priority: 64
          IPv4 Interface Address: 10.1.1.2
          IPv6 Interface Address: fe80::1:ff:fe0d:0
          Areas:
            49.0001
      Interface Ethernet30:
        Index: 36 SNPA: 0:1c:73:c:5:7f
        MTU: 1497 Type: broadcast
        Level 2:
          Metric: 10, Number of adjacencies: 1
          LAN-ID: 3030.3030.3030, Priority: 64
          DIS: 3030.3030.3030, DIS Priority: 64
        Adjacency 3030.3030.3030:
          State: UP, Level: 2 Type: Level 2 IS
          Hold Time: 9, Supported Protocols: ipv4, ipv6
          SNPA: 2:1:0:b:0:0, Priority: 64
          IPv4 Interface Address: 30.1.1.2
          IPv6 Interface Address: fe80::1:ff:fe0b:0
          Areas:
            49.0001
  • This example displays the state of TI-LFA protection for IPv4/IPV6 prefixes learned on that IS-IS interface.
    switch#show isis interface Vlan2387
    
    IS-IS Instance: inst1 VRF: default
    
      Interface Vlan2387:
        Index: 36 SNPA: P2P
        MTU: 1497 Type: point-to-point
        BFD IPv4 is Disabled
        BFD IPv6 is Disabled
        Hello Padding is Enabled
        Level 2:
          Metric: 10, Number of adjacencies: 1
          Link-ID: 24
          Authentication mode: None
          TI-LFA node protection with SRLG loose protection is enabled for the following IPv4 segments: node segments, adjacency segments
          TI-LFA protection is disabled for IPv6

show isis local-convergence-delay

The show isis local-convergence-delay command shows the current or last attempt at delaying the convergence of protected routes on a link down/BFD neighbor down event. If the timer aborts for some reason (such as a topology change causing a new SPF), the attempt fails.

switch#show isis local-convergence-delay 

IS-IS Instance: inst1 VRF: default
  System ID: 1111.1111.1001
  IPv4 local convergence delay configured, 5000 msecs
  IPv6 local convergence delay configured, 5000 msecs
  Level 1 attempts 0, failures 0
  Level 2 attempts 3, failures 1

  Level 2 in progress due to LINK DOWN on Vlan2138
    TI-LFA node protection is enabled for IPv4
    IPv4 Routes delayed: 0
      Delay timer started at: 2019-07-25 23:16:33
      Delay timer expires in 2 secs
    TI-LFA protection is disabled for IPv6

  Level 2 last attempt due to LINK DOWN on Vlan2138, Succeeded
    TI-LFA node protection is enabled for IPv4
    IPv4 Routes delayed: 3
      Delay timer started at: 2019-07-25 23:14:51
      Delay timer stopped at: 2019-07-25 23:14:56
    TI-LFA protection is disabled for IPv6

The detail keyword also lists all the routes that have been delayed.

switch#show isis local-convergence-delay detail
  ...
  Level 2 last attempt due to LINK DOWN on Vlan2138, Succeeded
    TI-LFA node protection is enabled for IPv4
    IPv4 Routes delayed: 3
      Delay timer started at: 2019-07-25 23:14:51
      Delay timer stopped at: 2019-07-25 23:14:56
      Delayed routes:
        10.0.7.1/32
        10.0.9.1/32
        10.0.10.1/32
    TI-LFA protection is disabled for IPv6

show isis neighbors

The show isis neighbors command displays IS-IS neighbor information.

Command Mode

EXEC

Command Syntax

show isis neighbors [INSTANCES] [INFO_LEVEL]

show isis neighbor [INFO_LEVEL] [VRF_INSTANCE]

Parameters
  • INSTANCES Options include:
    • no parameter
    • instance_name
  • INFO_LEVEL Options include:
    • no parameter
    • detail
  • VRF_INSTANCE Specifies the VRF instance.
    • no parameter
    • vrf vrf_name
Display Values
  • Inst. ID
  • System ID
  • Type
  • Interface
  • SNPA
  • State
  • Hold time
  • Area Address

Example

This command displays general information about the IS-IS neighbors.
switch(config)#show isis neighbors

Inst Id   System Id            Type Interface       SNPA              State Hold time
10        2222.2222.2222       L2   Vlan20          2:1:0:c:0:0       UP    30
10        1212.1212.1212       L2   Vlan20          2:1:0:d:0:0       UP    9
10        3030.3030.3030       L2   Ethernet30      2:1:0:b:0:0       UP    9
switch(config)#

show isis network topology

The show isis network topology command displays a list of all IS-IS devices that are reachable in the network.

Command Mode

EXEC

Command Syntax

show isis network topology

show isis INSTANCES network topology

show isis network topology VRF_INSTANCE

Parameter
  • INSTANCES Options include:
    • no parameter
    • instance_name
  • VRF_INSTANCE Specifies the VRF instance.
    • no parameter
    • vrf vrf_name
Display Values
  • System Id
  • Metric
  • Next-Hop
  • Interface
  • SNPA

Example

This command displays the list of all devices reachable in the network.
switch#show isis network topology

IS-IS Instance: Osiris VRF: default
  IS-IS paths to level-2 routers
    System Id        Metric   IA Metric Next-Hop         Interface     SNPA   
    2222.2222.2222   10       0         2222.2222.2222   Ethernet1     P2P 

switch>

show isis segment-routing adjacency-segments

The show isis segment-routing adjacency-segments command displays the global adjacency SID value and other related information.

Command Mode

EXEC

Command Syntax

show isis segment-routing adjacency-segments

Examples
  • In this example the show isis segment-routing adjacency-segments command displays the output for the interface configured like this:
    interface Ethernet1
     ip address 1.1.1.1/24
     ipv6 address 1000::1/64
     isis enable isis1
     isis network point-to-point
     adjacency-segment ipv4 p2p index 1 global
     adjacency-segment ipv6 p2p index 2 global
    
  • The show output for the above interface configuration:
    switch#show isis segment-routing adjacency-segments
    
    System ID: 1000.0000.0002                       Instance: isis1
    SR supported Data-plane: MPLS                   SR Router ID: 1.1.1.4
    Adj-SID allocation mode: SR-adjacencies
    Adj-SID allocation pool: Base: 100000     Size: 16384
    Adjacency Segment Count: 2
    Flag Descriptions: F: Ipv6 address family, B: Backup, V: Value
                      L: Local, S: Set
    
    Segment Status codes: L1 - Level-1 adjacency, L2 - Level-2 adjacency, P2P - 
    Point-to-Point adjacency, LAN - Broadcast adjacency
    
    Locally Originated Adjacency Segments
    Adj IP Address    Local Intf   SID     SID Source     Flags                Type        
    ----------------  ----------   ------  -------------  -------------------  -------
    1.1.1.2            Et1          1       Configured    F:0 B:0 V:0 L:0 S:0  P2P L1
    fe80::1:ff:fe65:0  Et1          2       Configured    F:1 B:0 V:0 L:0 S:0  P2P L1
    
    
    Received Global   Adjacency Segments
    SID               Originator               Neighbor           Flags     
    ---------         --------------------     ----------------   --------------------
    0                 rtrmpls1                 1000.0000.0002      F:0 B:0 V:0 L:0 S:0
    
  • The following is the C-API output for the show isis segment-routing adjacency-segments command.
    switch#show isis segment-routing adjacency-segments | json
    {
       "vrfs": {
           "default": {
               "isisInstances": {
                   "isis1": {
                       "routerId": "1.1.1.4",
                       "adjSidPoolSize": 16384,
                       "receivedGlobalAdjacencySegments": [
                           {
                               "systemId": "1000.0000.0001",
                                "hostname": "rtrmpls1",
                               "sid": 0,
                               "flags": {
                                   "s": false,
                                   "b": false,
                                   "v": false,
                                   "f": false,
                                   "l": false
                               },
                               "nbrSystemId": "1000.0000.0002"
                           }
                       ],
                       "systemId": "1000.0000.0002",
                       "adjSidAllocationMode": "SrOnly",
                       "dataPlane": "MPLS",
                       "adjacencySegments": [
                           {
                               "lan": false,
                               "sidOrigin": "configured",
                               "flags": {
                                   "s": false,
                                   "b": false,
                                   "v": true,
                                   "f": false,
                                   "l": false
                               },
                               "sid": 1,
                               "localIntf": "Ethernet1",
                               "ipAddress": "1.1.1.2",
                               "level": 1
                           },
                            {
                               "lan": false,
                               "sidOrigin": "configured",
                               "flags": {
                                   "s": false,
                                   "b": false,
                                   "v": false,
                                   "f": true,
                                   "l": false
                               },
                               "sid": 2,
                               "localIntf": "Ethernet1",
                               "ipAddress": "fe80::1:ff:fe65:0",
                               "level": 1
                           }
                       ],
                       "adjSidPoolBase": 100000,
                       "misconfiguredAdjacencySegments": []
                   }
               }
           }
       }
  • switch#show isis segment-routing adjacency-segments 
    ...
    Locally Originated Adjacency Segments
     Adj IP Address      Local Intf     SID          Flags                 Protection 
    -----------------    ----------     --------     --------------------- ------------ 
     10.1.0.1            Vl2138         100001       F:0 B:1 V:1 L:1 S:0    node 
     10.1.0.2            Vl2968         100002       F:0 B:1 V:1 L:1 S:0    node with SRLG loose
     10.1.0.3            Vl2387         965537       F:0 B:1 V:1 L:1 S:0    node with SRLG strict 
    
    
    Received Global Adjacency Segments
    SID       Originator            Neighbor            Flags                     Protection 
    --------- -------------------- -------------------- ------------------------- ---------- 
    5         1111.1111.1005        1111.1111.1004       F:0 B:1 V:0 L:0 S:0       node 

show isis segment-routing global-blocks

The show isis segment-routing global-blocks command lists the SRGBs in use by all SR supporting devices in IS-IS domain including the SRGB in use by IS-IS SR on this device.

Command Mode

EXEC

Command Syntax

show isis segment-routing global-blocks

Example
switch#show isis segment-routing global-blocks
System ID: 1111.1111.1002              Instance: inst1
SR supported Data-plane: MPLS          SR Router ID: 252.252.2.252
SR Global Block( SRGB ): Base: 900000  Size: 65536
Number of ISIS segment routing capable peers: 3
SystemId             Base         Size
-------------------- ------------ ----- 
1111.1111.1002       900000       65536
1111.1111.1001       900000       65536

show isis segment-routing prefix-segments

The show isis segment-routing prefix-segments command provides the details of all prefix segments being originated as well the segments received from IS-IS SR speakers in the domain.

Command Mode

EXEC

Command Syntax

show isis segment-routing prefix-segments

Example
switch#show isis segment-routing prefix-segments
System ID: 1111.1111.1002         Instance: inst1
SR supported Data-plane: MPLS     SR Router ID: 252.252.2.252
Node: 2 Proxy-Node: 2 Prefix: 2 Total Segments: 6
Flag Descriptions: R: Re-advertised, N: Node Segment, P: no-PHP
                   E: Explicit-NULL, V: Value, L: Local
Segment status codes: * - Self originated Prefix, L1 - level 1, L2 - level 2
    Prefix     SID     Type        Flags                    SystemID         Type
--------------------- ---------    -----------------------  ---------------  ----- 
 1.0.7.1/32      2     Node        R:0 N:1 P:0 E:0 V:0 L:0   1111.1111.1001   L1
* 1.0.8.1/32     4     Node        R:0 N:1 P:0 E:0 V:0 L:0   1111.1111.1002   L2
 1.0.11.0/24    10     Prefix      R:1 N:0 P:0 E:0 V:0 L:0   1111.1111.1001   L2
* 1.0.12.0/24   12     Prefix      R:1 N:0 P:0 E:0 V:0 L:0   1111.1111.1002   L2
 1.0.15.1/32    18     Proxy-Node  R:0 N:0 P:0 E:0 V:0 L:0   1111.1111.1001   L2
 1.0.16.1/32    20     Proxy-Node  R:0 N:0 P:0 E:0 V:0 L:0   1111.1111.1003   L2
switch#show isis segment-routing prefix-segments
...
  Prefix            SID   Type          System ID       Level  Protection
  -------------     ----- ------ ...    --------------- ------ ----------- 
* 10.1.1.1/32        0    Node   ...    1111.1111.1001   L2    unprotected
  10.1.1.2/32        1    Node   ...    1111.1111.1002   L2    node with SRLG loose
  10.1.1.3/32        4    Node   ...    1111.1111.1005   L2    node with SRLG strict
  10.1.1.4/32        10   Prefix ...    1111.1111.1004   L1    node

About the Output

After the usual output header that represents the system ID, instance name, etc and parameters of a router, there is a line depicting prefix segment counters. Each field in this line relates to the number of segments that are present in this routers IS-IS instance. For example, the above example shows that this device has 2 Node Segments (Self originated as well as the ones received from other IS-IS SR devices).

The main section of this show commands output is the section that lists all the prefix segments and related information like prefix, SID, type of segment (Prefix, Node, Proxy-Node), the flag values being carried in the sub-TLVs of these prefix segments and the system ID of the originating router. The Type field will be useful on a IS type level-1-2 router. It shows whether the installed prefix segment is from a level-1 prefix or a level-2 prefix.

show isis segment-routing

The show isis segment-routing command displays the summary information on IS-IS SR status.

Command Mode

EXEC

Command Syntax

show isis segment-routing

Example

The command output displays the summary information on IS-IS SR status.
switch(config)#show isis segment-routing
System ID: 1111.1111.1002               Instance: inst1
SR supported Data-plane: MPLS           SR Router ID: 252.252.2.252
SR Global Block( SRGB ): Base: 900000   Size: 65536
Adj-SID allocation mode: SR-adjacencies
Adj-SID allocation pool: Base: 100000     Size: 16384
All Prefix Segments have    : P:0 E:0 V:0 L:0
All Adjacency Segments have : F:0 B:0 V:1 L:1 S:0
ISIS Reachability Algorithm : SPF (0)
Number of ISIS segment routing capable peers: 3
Self-Originated Segment Statistics:
Node-Segments       : 2
Prefix-Segments     : 2
Proxy-Node-Segments : 0
Adjacency Segments :
About the Output

The first line of the output shows the IS-IS system ID of this device and the name of the instance with which IS-IS is configured.

The supported data plane is shown against the SR supported Data-plane field, while the router ID being advertised in the Router Capability is mentioned in the SR Router ID field.

The SRGB in use and the MPLS label pool being used for adjacency segment allocation are mentioned in this output. The current adjacency allocation mode which refers to whether we are allocating adjacency segments to all IS-IS adjacencies or only those adjacencies which support SR or None of the adjacencies is shown in the Adj-SID allocation mode field.

Flag contents of All Prefix Segments originated on this router, Flag contents of All Adjacency Segments originated on this router and supported IS-IS Reachability Algorithm have been provided through this command output and they carry the meaning as per the IS-IS SR IETF draft.

This show command provides a statistics related to IS-IS SR in terms of various counters ranging from number of IS-IS SR enabled peers, number of Node-SIDs, prefix-SIDs, proxy-node-segments and adjacency segments being originated on this router in IS-IS.

The show isis segment-routing command also provides information if segment routing has been administratively disabled as shown.
switch(config-router-isis-sr-mpls)#show isis segment-routing 
! IS-IS (Instance: inst1) Segment Routing has been administratively shutdown.

show isis segment-routing tunnel

The show isis segment-routing tunnel command displays all the IS-IS SR tunnels. The field TI-LFA tunnel index displays the index of the TI-LFA tunnel protecting the SR tunnel. The same TI-LFA tunnel that protects the LFIB route also protects the corresponding IS-IS SR tunnel.

switch#show isis segment-routing tunnel 10.0.10.1/32
Index   Endpoint        Nexthop    Interface   Labels     TI-LFA       
                                                          tunnel index 
------ --------------- ----------- ----------- ---------- -------------      
4       10.0.10.1/32    10.0.0.2   Vlan2387    [900004]   0  

show isis summary

The show isis summary command displays information about the configured IS-IS instances.

Command Mode

EXEC

Command Syntax

show isis summary

show isis [INSTANCES] summary

show isis summary VRF_INSTANCE

Parameters
  • INSTANCES Options include:
    • no parameter
    • instance_name
  • VRF_INSTANCE Specifies the VRF instance.
    • no parameter
    • vrf vrf_name
Display Values
  • System ID
  • IPv4 Preference
  • IPv6 Preference
  • IS-Types
  • LSP Generation interval
  • SPF Interval
  • Current SPF Hold Interval
  • IS-Types Run Time
  • Area Addresses
  • Designated Intermediate Systems (DIS) Interfaces
  • Link State DataBase (LSDB) size
Display Status
  • Multi Topology
  • Authentication Mode
  • Graceful Restart
  • Graceful Restart Helper

Example

This command displays general information about the configured IS-IS instances.
switch(config-router-isis-af)#show isis summary

IS-IS Instance: 1 VRF: default
 System ID: 0000.0000.0001, administratively enabled
 Multi Topology disabled, not attached
 IPv4 Preference: Level 1: 115, Level 2: 115
 IPv6 Preference: Level 1: 115, Level 2: 115
 IS-Type: Level 1 and 2, Number active interfaces: 0
 Routes both IPv4 and IPv6
 LSP size maximum: Level 1: 9000, Level 2: 9000
                           Max wait(s) Initial wait(ms) Hold interval(ms)
 LSP Generation Interval:     5              50               50
 SPF Interval:                2            1000             1000
 Current SPF hold interval(ms): Level 1: 1000, Level 2: 1000
 Last Level 1 SPF run 1 seconds ago
 Last Level 2 SPF run 1 seconds ago
 Authentication mode: Level 1: None, Level 2: None
 Graceful Restart: Disabled, Graceful Restart Helper: Enabled
 Area Addresses:
   49.0001
 level 1: number dis interfaces: 0, LSDB size: 1
 level 2: number dis interfaces: 0, LSDB size: 1

show isis ti-lfa path

The show isis ti-lfa path command displays the repair path with the list of all the system IDs from the P-node to the Q-node for every destination/constraint tuple. You will see that even though node protection is configured, a link protecting LFA is computed too. This is to fallback to link protecting LFAs if the node protecting LFA becomes unavailable.

switch#show isis ti-lfa path 1111.1111.1005
TI-LFA paths for IPv4 address family
Topo-id: Level-2
Destination     Constraint                     Path           
1111.1111.1005  exclude node 1111.1111.1002    1111.1111.1003 
                                               1111.1111.1004 
                exclude Vlan2387               1111.1111.1002
                SRLG strict	

 

switch#show isis ti-lfa path 10.10.10.1/32
TI-LFA paths for IPv4 address family
Topo-id: Level-1
Destination     Constraint                   Path
--------------- ---------------------------- --------------
10.10.10.1/32   exclude Vlan2387             1111.1111.1002
                                             1111.1111.1003
                exclude node 1111.1111.1004  1111.1111.1002
		  SRLG strict		     1111.1111.1003

show isis ti-lfa tunnel

The TI-LFA repair tunnels are just internal constructs that are shared by multiple LFIB routes that compute similar repair paths. The show isis ti-lfa tunnel command displays TI-LFA repair tunnels with the primary and backup via information.

switch#show isis ti-lfa tunnel 1
Tunnel Index 1
   via 10.0.1.2, 'Vlan2968'
      label stack 3
   backup via 10.0.0.2, 'Vlan2387'
      label stack 900004 900002

show mpls label ranges

The show mpls label ranges command displays the MPLS label range available on a router is categorized into different pools which cater to different applications running on the router.

Command Mode

EXEC

Command Syntax

show mpls label ranges

Example
switch#show mpls label ranges
Start    End      Size     Usage
-----------------------------------------
0        15       16       reserved
16       99999    99984    static mpls
100000   116383   16384    isis (dynamic)
116384   362143   245760   free (dynamic)
362144   899999   537856   unassigned
900000   965535   65536    isis-sr 

show mpls lfib route <label value>

The show mpls lfib route command provides information relevant to just the label value passed as an extension to the show command.

Command Mode

EXEC

Command Syntax

show mpls lfib route label value

Example
switch#show mpls lfib route 900008
MPLS forwarding table (Label [metric] Vias) - 7 routes
MPLS next-hop resolution allow default route: False
Via Type Codes:
        M - Mpls Via, P - Pseudowire Via,
        I - IP Lookup Via, V - Vlan Via,
        VA - EVPN Vlan Aware Via, ES - EVPN Ethernet Segment Via,
        VF - EVPN Vlan Flood Via, AF - EVPN Vlan Aware Flood Via,
        NG - Nexthop Group Via
Source Codes:
        S - Static MPLS Route, B2 - BGP L2 EVPN,
        B3 - BGP L3 VPN, R - RSVP,
        P - Pseudowire, L - LDP,
        IP - IS-IS SR Prefix Segment, IA - IS-IS SR Adjacency Segment,
        IL - IS-IS SR Segment to LDP, LI - LDP to IS-IS SR Segment,
        BL - BGP LU, ST - SR TE Policy,
        DE - Debug LFIB
 IP 900008 [1]
            via M, 1.0.1.2, swap 900008
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930

show mpls lfib route

The show mpls lfib route command displays the LFIB. Each LFIB entry has In-Label, Out-Label, metric, payload type, nexthop information, etc. fields. The source column depicts the MPLS control plane protocol that is responsible for the label binding that resulted in this LFIB route.

Command Mode

EXEC

Command Syntax

show mpls lfib route

Example
switch#show mpls lfib route
MPLS forwarding table (Label [metric] Vias) - 7 routes
MPLS next-hop resolution allow default route: False
Via Type Codes:
        M - Mpls Via, P - Pseudowire Via,
        I - IP Lookup Via, V - Vlan Via,
        VA - EVPN Vlan Aware Via, ES - EVPN Ethernet Segment Via,
        VF - EVPN Vlan Flood Via, AF - EVPN Vlan Aware Flood Via,
        NG - Nexthop Group Via
Source Codes:
        S - Static MPLS Route, B2 - BGP L2 EVPN,
        B3 - BGP L3 VPN, R - RSVP,
        P - Pseudowire, L - LDP,
        IP - IS-IS SR Prefix Segment, IA - IS-IS SR Adjacency Segment,
        IL - IS-IS SR Segment to LDP, LI - LDP to IS-IS SR Segment,
        BL - BGP LU, ST - SR TE Policy,
        DE - Debug LFIB
 IA 100000 [1]
            via M, 1.0.1.2, pop
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930
 IA 100001 [1]
            via M, fe80::200:eff:fe02:0, pop
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930
 IP 900008 [1]
            via M, 1.0.1.2, swap 900008
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930
 IP 900009 [1]
            via M, fe80::200:eff:fe02:0, swap 900009
            payload autoDecide, ttlMode uniform, apply egress-acl
            interface Vlan2930

show mpls segment-routing bindings

The show mpls segment-routing bindings command displays the local label bindings and label bindings on the peer routers for each prefix that has a segment advertised. Peer ID here represents the IS-IS system ID of the peer.

Command Mode

EXEC

Command Syntax

show mpls segment-routing bindings

Example
switch#show mpls segment-routing bindings
1.0.7.1/32
 Local binding: Label: 900002
 Remote binding: Peer ID: 1111.1111.1001, Label: imp-null
 Remote binding: Peer ID: 1111.1111.1003, Label: 900002
1.0.8.1/32
 Local binding: Label: imp-null
 Remote binding: Peer ID: 1111.1111.1001, Label: 900004
 Remote binding: Peer ID: 1111.1111.1003, Label: 900004
1.0.9.1/32
 Local binding: Label: 900006
 Remote binding: Peer ID: 1111.1111.1001, Label: 900006
 Remote binding: Peer ID: 1111.1111.1003, Label: imp-null

show tunnel fib

The show tunnel fib command that displays tunnels programmed in the tunnel FIB also includes the TI-LFA tunnels along with protected IS-IS SR tunnels.

switch#show tunnel fib ti-lfa 1

Type 'TI-LFA', index 1, forwarding None
   via 10.0.1.2, 'Vlan2968'
      label stack 3
   backup via 10.0.0.2, 'Vlan2387'
      label stack 900004 900002

 

switch#show tunnel fib isis segment-routing 

Type 'IS-IS SR', index 1, endpoint 2002::b00:201/128, forwarding Primary
   via TI-LFA tunnel index 3 label 3
      via fe80::200:76ff:fe01:0, 'Ethernet30/1' label 900002
      backup via fe80::200:76ff:fe03:0, 'Ethernet26/1' label 132769

Type 'IS-IS SR', index 2, endpoint 2002::b00:101/128, forwarding Primary
   via TI-LFA tunnel index 4 label 3
      via fe80::200:76ff:fe01:0, 'Ethernet30/1' label 3
      backup via fe80::200:76ff:fe03:0, 'Ethernet26/1' label 132769 900001

shutdown (IS-IS SR)

The shutdown and default shutdown commands administratively disable IS-IS SR on the switch without modifying the IS-IS SR configuration.

The no shutdown command enables IS-IS SR.

Command Mode

Segment-Routing MPLS Configuration

Command Syntax

shutdown

no shutdown

default shutdown

Examples
  • These commands administratively disable IS-IS SR on the switch but preserve the IS-IS SR configuration.
    switch(config)#router isis Osiris
    switch(config-router-isis)#segment-routing mpls
    switch(config-router-isis-sr-mpls)#shutdown
    switch(config-router-isis-sr-mpls)#
  • This command enables IS-IS SR on the switch.
    switch(config)#router isis Osiris
    switch(config-router-isis)#segment-routing mpls
    switch(config-router-isis-sr-mpls)#no shutdown
    switch(config-router-isis-sr-mpls)#

shutdown (IS-IS)

The shutdown command disables IS-IS on the switch without modifying the IS-IS configuration.

The no shutdown and default shutdown commands enable the IS-IS instance by removing the shutdown command from running-config.

Command Mode

Router-IS-IS Configuration

Command Syntax

shutdown

no shutdown

default shutdown

Examples
  • These commands disable IS-IS on the switch.
    switch(config)#router isis Osiris
    switch(config-router-isis)#shutdown
    switch(config-router-isis)#
  • This command enables IS-IS on the switch.
    switch(config)#router isis Osiris
    switch(config-router-isis)#no shutdown
    switch(config-router-isis)#

spf-interval

The spf-interval command sets the Shortest Path First (SPF) timer that defines the interval between IS-IS path calculations. The default value is two seconds.

This command also configures the maximum wait interval between any two SPF runs, initial wait interval before executing the first SPF computation, and the hold time between the first and second SPF runs.

The no spf-interval and default spf-interval commands restore the default maximum IS-IS path calculation interval to two seconds by removing the spf-interval command from running-config.

For information about viewing SPF interval values, see Displaying IS-IS Instance Information.

Command Mode

Router-IS-IS Configuration

Command Syntax

spf-interval max-wait [initial-wait | hold-time]

no spf-interval

default spf-interval

Parameters
  • max-wait Value ranges from 1 through 300 seconds. Default maximum wait interval is 2 seconds.
  • initial-wait Value ranges from 1 through 300000 ms. Default initial wait interval is 1000 ms.
  • hold-time Value ranges from 1 through 300000 ms. Default hold interval is 1000 ms.

Guidelines

EOS does not support configuring topology-specific SPF timers in multi-topology deployments and IS-IS level-specific SPF timers.

Examples

  • This command configures the SPF maximum wait interval to 50 seconds.
    switch(config)#router isis Osiris
    switch(config-router-isis)#spf-interval 50
  • This command configures maximum wait interval, initial wait interval, and hold time to 20 seconds, 10000 ms, and 5000 ms respectively.
    switch(config)#router isis inst1
    switch(config-router-isis)#spf-interval 20 10000 5000
  • This command reverts the SPF interval configuration to its default value.
    switch(config)#router isis Osiris
    switch(config-router-isis)#no spf-interval