Configure Backup Routing on Tenant VRF

Enable backup routing when all the links from a leaf device to the spine layer are down, and tenant traffic is to be routed via the MCT neighbor.

IPv4 and IPv6 range are the input at the fabric level. A pair of IPv4 and IPv6 address is allocated to each MCT pair across all the tenant VRFs, and the BGP session is established between the same IP Pair.

Allocate a pair of IPv4 and IPv6 address to each MCT pair across all the tenant VRFs.
1. Allocate a Bridge domain per VRF for backup routing.
2. Allocate a corresponding router-interface VE per BD or VRF.
3. Assign the IPv4 and IPv6 address allocated to each device on each of the VE interface.
  
  Note
  Same IPv4 and IPv6 address is allocated on each of the VE interface which belongs to different VRF.
4. Establish IBGP IPv4 neighborship with the MCT peer on a set of IP address per VRF.
5. Establish IBGP IPv6 neighborship with the MCT peer on a set of IPv6 address per VRF.
6. Configure "next-hop-self" on both the IPv4 and IPv6 neighbor.
7. Configure "active" on the IPv6 neighbor.
Example:
```
efa fabric setting update --name fabric1
--backup-routing-ipv4-range 21.1.1.0/24 --backup-routing-ipv6-range 2001:21:1:1::0/120
```
Example when backup routing is enabled:
```
efa fabric setting update --name nc --backup-routing-enable yes
```

Configure devices on tenant VRFs.

Table 1. Tenant1 VRF “vrf1”

leaf-9250-173# show running-config bridge-domain 3001 bridge-domain 3001 p2mp pw-profile default router-interface Ve 7001 bpdu-drop-enable ! leaf-9250-173# sh run in ve 7001 interface Ve 7001 vrf forwarding vrf1 ip address 21.1.1.10/31 ipv6 address 2001:21:1:1::10/127 no shutdown !	leaf-9250-173# show running-config router bgp address-family ipv4 unicast vrf vrf1 router bgp address-family ipv4 unicast vrf vrf1 local-as 4210000001 redistribute connected neighbor 21.1.1.11 remote-as 4210000001 neighbor 21.1.1.11 next-hop-self maximum-paths 2 ! ! leaf-9250-173# show running-config router bgp address-family ipv6 unicast vrf vrf1 router bgp address-family ipv6 unicast vrf vrf1 redistribute connected neighbor 2001:21:1:1::11 next-hop-self neighbor 2001:21:1:1::11 remote-as 4210000001 neighbor 2001:21:1:1::11 activate maximum-paths 2 ! !

Table 2. Tenant2 VRF “vrf2”

leaf-9250-173# show running-config bridge-domain 3002 bridge-domain 3002 p2mp pw-profile default router-interface Ve 7002 bpdu-drop-enable ! leaf-9250-173# sh run in ve 7002 interface Ve 7002 vrf forwarding vrf2 ip address 21.1.1.10/31 ipv6 address 2001:21:1:1::10/127 no shutdown !	leaf-9250-173# show running-config router bgp address-family ipv4 unicast vrf vrf2 router bgp address-family ipv4 unicast vrf vrf2 local-as 4210000001 redistribute connected neighbor 21.1.1.11 remote-as 4210000001 neighbor 21.1.1.11 next-hop-self maximum-paths 2 ! ! leaf-9250-173# show running-config router bgp address-family ipv6 unicast vrf vrf2 router bgp address-family ipv6 unicast vrf vrf2 redistribute connected neighbor 2001:21:1:1::11 next-hop-self neighbor 2001:21:1:1::11 remote-as 4210000001 neighbor 2001:21:1:1::11 activate maximum-paths 2 ! !