Cisco NAT for exchange 2010
Posted on 2011-09-19
All, I have a cisco 1800 series router that I need to have an exchange server behind. It's running IOS without the firewall enabled, rather, access is more or less turned off or on on a one by one basis.
I have an exchange server with the proper MX and A records at the ISP level. The current configuration worked previously by doing a NAT translation inside and out like this:
ip nat pool exchange 192.168.1.7 192.168.1.7 netmask 255.255.255.255
ip nat inside source static network 192.168.1.7 220.127.116.11 /32
ip nat outside source static network 18.104.22.168 192.168.1.7 /32
This configuration worked with the Cisco 831 for over a year. We did get an occasional IP conflict error when we had an outage and came back up, but I was always able to program around it by changing the NAT to another internal IP, then bringing up the server, then changing it back. I realize this was a redneck solution, but it did work and I figured I'd figure out the issue later.
Later is now.
When we replaced the 831with a cisco 1800, it reports an IP conflict. at both the router, and server. The NAT translation is using the address and the exchange server shows as 'no internet access' as you would expect from an IP conflict. It is not resolveable by the workaround I previously mentioned. The newer router is far less tolerant, it seems, of this kind of NAT/IP conflict.
I have no idea how it worked before given what I now know. However, I'm not at all sure how to fix this going forward. what is the correct way to make this work, using the IP information above? I need to be sure that OWA access is available inside and outside the internal network, and that direct access through outlook is available internally. Help!