Network Warrior, 2nd Edition

Virtual Routing and Forwarding

Nexus switches and newer versions of IOS support something called Virtual Routing and Forwarding (VRF) instances. Each VRF is a self-contained routing table within the same router. Within a Nexus 7000, you can have multiple VRFs within a single Virtual Device Context (VDC). On the Nexus 5000, which as of this writing does not support VDCs or routing, you can still have multiple VRFs. In fact, by default, the management network resides in a management VRF, while other traffic is in the default VRF. In IOS 15.x, you may also configure VRFs.

On the Nexus platform, two VRFs exist by default—management and default:

NX-7K-1-Daisy# sho vrf
VRF-Name                    VRF-ID    State   Reason
default                          1    Up      --
management                       2    Up      --

Creating a new VRF is as simple as specifying one with the vrf context vrf-name command. Here, I’ll create two new VRFs, named Earth and Mars:

NX-7K-1-Daisy(config)# vrf context Earth
NX-7K-1-Daisy(config)# vrf context Mars

Now we can see the additional VRFs with the show vrf command:

NX-7K-1-Daisy(config)# sho vrf
VRF-Name                    VRF-ID    State   Reason
Earth                            3    Up      --
Mars                             5    Up      --
default                          1    Up      --
management                       2    Up      --

Interfaces can be assigned to VRFs. Remember that in Nexus 7000 switches, interfaces default to routed mode, so we don’t need to configure them as such. You apply interfaces to VRFs with the vrf member vrf-name interface command:

NX-7K-1-Daisy(config)# int e3/25
NX-7K-1-Daisy(config-if)# vrf member Earth
NX-7K-1-Daisy(config-if)# ip address 10.0.0.1/24

Now I’ll assign ...