# Configuring Secondary Routing Table Lookup

You can enable secondary routing table lookup on the virtual router routing table of the parent (global) virtual router. The secondary lookup takes place when the initial route lookup on a VRF is unsuccessful. You can define secondary routing table lookup outside the context of the VRF or inside the context of the VRF.

To configure secondary routing table lookup from outside the VRF context:

1. Select the interface.
   host1:vr1(config)#interface gigabitEthernet 1/0
2. Specify a VRF and that you want it to perform secondary routing table lookup.
   host1:vr1(config-if)#ip vrf forwarding vrfA fallback global host1:vr1:vrfA(config-if)#ip address 10.12.4.5 255.255.255.0

To specify from inside the VRF context that an interface use the fallback global routing table lookup:

1. Select the interface.
   host1:vr1(config)#interface gigabitEthernet 1/0
2. Enter the VRF context.
   host1:vr1(config-if)#virtual-router :vrfA
3. Specify that the VRF perform a secondary routing table lookup.
   host1:vr1:vrfA(config-if)#ip fallback global

#### Related Documentation

- ip fallback global
- ip vrf forwarding