vPC VXLAN BGP EVPN Advance Feature

Using vPC Peer Link as an Underlay Backup Path

Here we will see , how the VTEP switch can use a vPC peer link as a backup path to Spine switch in a situation where the Leaf switch loses connection to the Spine switch. This is recommended redundancy model when using vPC in VXLAN BGP EVPN fabric. For simplicity, there is only one spine switch used in example network.

Inter-Switch links use Unnumbered IP addressing (Loopback 0). Underlay unicast routing protocol is OSPF and PIM BiDir is used for Layer 2 BUM traffic. These two protocols are also needed in Inters-switch links between vPC peers in Backup Path solution.

Configuration

Step 1: Create VLAN 99

Step 2: Create Interface VLAN 99 an assign the IP address to it.

Step 3: Enable ospf and set link type to P2P in VLAN interface (we do not need DR/BDR election here)

Step 4: Enable PIM-SM on Interface VLAN 99

Note! Port-channel 23 (Trunk) is used as a vPC Peer-Link and VLANs 1-4094 are allowed in it.

VLAN 99 is used for establishing the Backup Underlay Network connection over the vPC Peer-Link. VLAN 99 is not a client VLAN (not mapped to any L2VNI) but an infra VLAN, which is why the command “system nve infra-vlans 99” is required when using physical Nexus switches. NX-OSv is used in this example, and it does not have that command.