BGP EVPN VXLAN
Creating a BGP EVPN VXLAN fabric: spine-leaf switching with a modern overlay control plane.
Overview
This lab builds a compact data-centre fabric the way modern campuses and clouds run it: two spines, two leaf pairs, and NX-OS virtual switches hosting the tenants. OSPF forms the underlay so every loopback can reach every other loopback, then MP-BGP EVPN advertises MAC and IP reachability between the leaves.
VXLAN carries the tenant frames across that underlay, which means new segments are created with configuration only — no recabling, no spanning-tree redesign, no maintenance window for the physical fabric.
Lab facts
- PlatformEVE-NG · NX-OS
- UnderlayOSPF, /32 loopbacks
- OverlayMP-BGP EVPN
- Data planeVXLAN, flood-and-learn
- Fabric2 spines · 4 leaves
What this lab covers
- Spine-leaf cabling with OSPF unnumbered underlay links
- MP-BGP EVPN peering from every leaf to both spines
- NVE interfaces binding VLANs to VXLAN VNIs
- Anycast gateway so hosts share one default route
- Host mobility test: moving a VM between leaves
- Spine loss drill with traffic reconverging via the survivor
Key configuration
! Leaf — EVPN neighbour to both spines router bgp 65011 neighbor 10.0.0.1 remote-as 65011 update-source loopback0 address-family l2vpn evpn neighbor 10.0.0.1 activate ! NVE — VLAN 20 rides VNI 10020 with anycast gateway interface nve1 no shutdown source-interface loopback1 member vni 10020 mcast-group 239.1.1.20 interface vlan20 ip address 192.168.20.1/24 fabric forwarding mode anycast-gateway
Results & takeaways
Hosts on the same segment but different leaves communicated at Layer 2 through the overlay, and the moved VM kept its address and gateway after migrating leaves — EVPN simply re-advertised the MAC from the new location. Losing a spine halved the paths but dropped no tenant traffic.
The main lesson: the underlay deserves as much care as the overlay. One mistyped loopback broke EVPN peering in a way that looked exactly like a VXLAN fault — verifying underlay reachability first would have found it in minutes.