Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Two Routers:
Router A:

  1. F0/0 with a public IP to the internet:
  2. F1/0 which is a LAN:
  3. S0 which is one of a point to point connection:

Router B:

  1. S1 which is the other end of the point to point
  2. F2/0 which is the LAN:

How can I set up nat (overloading) so that traffic from router B (The Lan) can use the F0/0 internet connection on router A?

Is it all done on router A?

I would think it works like this: I just set F0/0 to nat outside, and S0 to nat inside, and add the 192.168.1.* network to the ACL for the nat overload rule? But I never done this set up before...

share|improve this question
up vote 2 down vote accepted

You're on the right track. Yes, it is all done on Router A. You will want both F1/0 and S0 to have ip nat inside on them. The ACL on Router A's ip nat inside source command should include both 10.10.10.x and one of the following:

  1. If Router B is doing NAT on its own, so Router A only ever sees traffic from, you need to add (or to the ACL.
  2. If Router B is not doing NAT, (which it probably isn't), then you need to add 10.10.20.x to the ACL (and probably also if Router B needs to talk to the Internet).

Basically, the ACL just needs to cover any source IP you want to NAT as it appears to Router A when it enters an interface with ip nat inside on it. Traffic from the Router B LAN will be seen by Router A as 10.10.20.x (unless Router B does its own NAT overload).

share|improve this answer
Ya, router B will not being do NAT, but good thinking! This all makes sense to me, thank you. – Kyle Brandt Oct 6 '09 at 19:32

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.