VXLAN Underlay Routing - Part IV: Two-AS eBGP

Now you can also download my VXLAN book from the Leanpub.com 

"Virtual Extensible LAN VXLAN - A Practical guide to VXLAN Solution Part 1. (373 pages)

eBGP as an Underlay Network Routing Protocol: Two-AS eBGP

This post explains the Two-AS eBGP solution in VXLAN Fabric, where there is single AS Area for all Leaf switches and other AS Area for all Spine switches. It also discusses how the default operating model used in eBGP peering has to be modified in order to achieve a routing solution required by VXLAN Fabric. These modifications are mainly related to BGP loop prevention model and BGP next-hop path-attribute processing.

Figure 1-1 illustrates the topology used in this chapter. Leaf-101 and Leaf-102 both belong to BGP AS 65000, while Spine-11 belongs to BGP AS 65099. Loopback interfaces used for Overlay Network BGP peering (L100) and for NVE peering (L50) are advertised over BGP AFI IPv4 peering (Underlay Network Control Plane). Host MAC/IP address information is advertised over BGP AFI L2VPN EVPN peering (Overlay Network Control Plane). Ethernet frames between host Café and Abba are encapsulated with a VXLAN tunnel header where the source and destination IP addresses used in the outer IP header are taken from NVE1 interfaces.

Figure 1-1: High-Level operation of VXLAN Fabric