A “path” represents a pair of interfaces (or their IP addresses), a source interface and a destination interface through which traffic can flow from site to site.
For example, in the above figure there are two paths from Router1 to Router2
- MPLS path - 172.16.1.1 -- 172.16.2.1
- 4 Internet paths
- 220.127.116.11 -- 18.104.22.168
- 22.214.171.124 -- 126.96.36.199
- 188.8.131.52 -- 184.108.40.206
- 220.127.116.11 -- 18.104.22.168
However, some of the paths are crossing ISPs, for example, 22.214.171.124 -- 126.96.36.199 is going from router1 through ISP1, ISP2 to router2. In some customer scenarios ISP2 could be an LTE SP and could be purely as a backup in case ISP1 fails. In this case the paths 188.8.131.52 -- 184.108.40.206 and 220.127.116.11 -- 18.104.22.168 should not be used.
Path-group similar to nexthop-group is used to group the paths in order to
- Restrict paths - define which paths are valid among the available paths like the LTE backup SP discussed before
- Apply specific policies to path group. Eg apply encryption for all Internet paths
Path group commands are configured under “router path-selection” as shown below. The commands are explained in the subsections.
router path-selection path-group <group-name> local interface <intf-name> ## more local interface commands ## that belong to the same path-group, eg Internet peer static router-ip <ip-address> ipv4 address <ip-addr1> ## more IP addresses through which the router can be reached
The router-IP is the same as the VTEP-IP. local is used to configure the local WAN IP address or interface part of the path-group. Peer is used to configure the remote VTEP reachability statically.
Each combination of peer and local IP address is a potential path. If routing resolves the remote IP through a local interface then that local-remote IP pair becomes a real path that is used for forwarding.
In the topology in the above figure two groups are defined.
Further if paths need to be restricted through the Internet, the Internet groups can be divided into more groups. For example, the customer can define ISP1 and ISP2-ISP3 as separate groups create 2 Internet paths instead of 4.