NAT pool and outside interface

When working with NAT, does the IP Address on my outside interface have to be part of the same subnet for my range of NAT pool IP Addresses? Or, can I have a configuration such as the following:

int s0/0/0
ip address
ip nat outside

int fa0/0
ip address
ip nat inside

ip access-list TEST2

ip nat pool TEST prefix-length 29
ip nat inside source TEST2 pool TEST overload

And if the subnet of my pool of IP Addresses can vary from the IP Address configured on s0/0/0, what about that configuration needs to be changed to allow a successful ping (and translation) from a device on my private LAN ( to the network?


It doesn’t have to be an IP address on your outside interface, you could use a different range in the pool.

There’s two things you should do though:

  • Create a loopback interface and configure the subnet there that you use in the pool.
  • Advertise this subnet or use a static route on the other side.