inside to inside NAT?

Unanswered Question
Apr 8th, 2008

I have a pretty standard NAT setup for a company with a small Cisco 871 WAN router:

int E0, IP=xxx.xx.xx.xx, ip nat outside

int Vlan1, IP=192.168.1.1 ip nat inside

one port forwarding rule:

ip nat inside source static tcp 192.168.1.20 110 xxx.xx.xx.xx 110 extendable

People have laptops set up with an email application that has the xxx.xx.xx.xx public IP hard-coded in it. It works fine outside "on the Internet", but when they bring their laptops into work, it doesn't work. Now, obviously, one solution is to change the hard-coding of the app to go to the Vlan1 IP of 192.168.1.20 instead the outside public IP of xxx.xx.xx.xx

But is there a way to do this with "ip nat" statements?

I tried an "ip nat outside static 192.168.1.20 xxx.xx.xx.xx" but that didn't work.

I have this problem too.
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Jason Fraioli Tue, 04/08/2008 - 11:23

sounds like the more logical approach would be to use split DNS to control that. From the outside the address of host.xyz.com = E0 (outside IP), but inside, the host.xyz.com = your 192.168.1.20 IP address.

Obviously this would require inside and outside DNS setup to accomplish this.

thomasdzubin Tue, 04/08/2008 - 11:32

Yes, using DNS was considered, but (since I'm the network guy) I don't control the DNS servers and I'd rather see if a simple NAT statement can fix what I need.

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