WAN Overlay using VXLAN

Note, that the routers are connected to two SPs in the above diagram. All customer prefixes are on the overlay network and if the VTEP IP r1addr and r2addr addresses are accessible through SP networks then the VXLAN overlay would work similar to the datacenter network. However the VTEP IP address is an internal IP address and is not routable over SP networks. While it is possible to make the VTEP IP address routable over MPS network (unlike ISP), since we want to dynamically load balance across SP networks we will not advertise the VTEP IP address over MPLS.

However, the WAN interfaces have SP routable IP address. For example, r1w1 IP address is routable on WAN1 and r1w2 IP address is routable on WAN2. The forwarding engine will replace the VTEP address on the packet based on the path selected before sending it to SP network.

Therefore for router 1:

  • The router VTEP IP V1 is the nexthop for all the customer prefixes and the customer prefixes p1, and others are advertised using EVPN type 5 address family.
  • VTEP IP V1 is reached through the two publically routable WAN IP addresses r1w1 address and r1w2 address.

For this, the router needs to know SP routable IP addresses through which it can reach each.