I am running a Cisco 831 with fastethernet 4 used as a DMZ port (ethernet 2). My ISP gave me a /29 network. Of the 6 usable IP's one is assigned to the ISP's device and one to ethernet 1 on my 831. Because of this, I am using static NAT to map the other 4 to the private IP's (172.17.1.0/24) of servers on the DMZ. One of the servers (172.17.1.3)is MX 10 for the domain and another (172.17.1.5) is MX 20 for the same domain. Everything works OK except for this:
When MX 20 (172.17.1.5) trys to forward email to MX 10, it performs a DNS lookup and receives the registered IP for MX 10 (69.2.x.x which is static NATed to 172.17.1
3). When it trys to connect to 69.2.x.x), the connection is refused. From MX 20, I can telnet to MX 10 "telnet 172.17.1.3 25" and connect, but if I go "telnet 69.2.x.x 25" the connection is refused.
I hope this explains the problem clearly. Does anyone have any suggestions as how I can work around this?
