"Virtual Extensible LAN VXLAN - A Practical guide to VXLAN Solution Part 1. (373 pages)
eBGP as an Underlay
Network Routing Protocol: Multi-AS eBGP
This post introduces the Multi-AS eBGP solution in VXLAN
Fabric. In this solution, a single AS number is assigned to all spine switches while
each leaf switches (or pair of leaf switches) have unique BGP AS number. This
solution neither requires “allowas-in” command in leaf switches nor
“disable-peer-check” command in the spine
switches, which are required in Two-AS solution. The “retain-route-target all” command and BGP L2VPN EVPN address family peer-specific route-map with an option “set ip next-hop-unchanged” is needed on the spine switch. This post also explains the requirements
and processes for L2 EVPN VNI specific route import policy when automated
derivation of Route-Targets is used. The same IP/MAC address scheme is used in
this chapter than what was used in the previous
post “VXLAN Underlay Routing - Part IV:
Two-AS eBGP” but the Leaf-102 now belongs to BGP AS 65001.
Figure 1-1: The MAC/IP
addressing scheme and eBGP peering model.
