strange inside-outside-inside PAT problem

Unanswered Question
Feb 24th, 2008
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I have a router with three interfaces serving two (related) companies. Each company has their own LAN interface but both share the WAN interface even though each company has a different public IP. I've set up standard NAT and incoming PAT rules and everything works just fine... EXCEPT I cannot get company1 to communicate to company2 if they use their external WAN IPs...

here's a sanitized snipped of the config:

interface FastEthernet0/0

description WAN

ip address

ip address secondary

ip nat outside


interface FastEthernet0/1

description LAN1

ip address

interface FastEthernet0/2

description LAN2

ip address

ip nat inside

ip route

ip nat inside source static tcp 25 25 extendable

ip nat inside source static tcp 25 25 extendable

If I try to connect to port 25 of company1's public IP from an internal LAN IP of company2 it doesn't work. I can connect internal 10.0.0.x and 192.168.0.x just fine, but using the other company's public IP doesn't work.

I'm guessing it's because I'm doing double NAT, but I don't know how to fix it.

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