Cisco weird interfaces

NVI - NAT Virtual Interface

Not everyone knows that from IOS version 12.3(14)T, Cisco has introduced a new feature called NAT Virtual Interface; NVI removes the requirements to configure an interface as either NAT inside or NAT outside. An interface can be configured to use NAT or not use NAT.

How to use NVI? It’s easy! You must use the command ‘ip nat source …’ without specifying the inside/outside tag and enable the nat to the interfaces using the command ‘ip nat enable’.

For instance, if you use legacy statement:

R1(config)#interface range fastEthernet 0/0
R1(config-if-range)#ip nat inside

R1(config)#interface range fastEthernet 0/1
R1(config-if-range)#ip nat outside

R1(config)#ip nat inside source static 172.16.0.6 10.16.0.5

with NVI feature the nat will be:

R1(config)#interface range fastEthernet 0/0
R1(config-if-range)#ip nat enable

R1(config)#interface range fastEthernet 0/1
R1(config-if-range)#ip nat enable

R1(config)#ip nat source static 172.16.0.6 10.16.0.5

References

• NAT Virtual Interface aka NVI, what is that?!