Virtual Routing and Forwarding is a technology which creates a separate virtual router inside of a physical router.
The virtual routers interfaces, routing and forwarding tables are completely isolated from the physical router and other virtual routers, preventing traffic from traversing from one virtual router to the other.
By default, all interfaces belong to the global VRF until they are re-assigned. This global VRF is identical to a router that does not partake or support VRF at all.
Each VRF instance maintains its own support routing table. This permits the router to overlap IP addresses across different VRFs.
To create a multiprotocol VRF instance; enter the following command in global configuration mode:
vrf definition vrfname
After entering the command, a sub-mode will be entered where the protocol can be selected, choosing between
address-family ipv4 or
With the VRF created, the command
vrf forwarding vrfname can be entered under interfaces in interface configuration mode to associate an interface with a VRF.
Many commands support an option of VRF to view specific command information associated with that VRF. For example:
show ip arp vrf vrfname or
show ip route vrf vrfname
If the vrf option is not specified, any information associated with that VRF will not display in the output of the command.