I'm having a problem when im doing NAT on dual-homing systems. I'll give an example, when i try to connect at some places TCP/25 behind the router, for some locations works (like gmail,etc) but there are some others SMTP servers that doesn't work. When i telnet from the router that same place that doesn't work behind the router, it works. I did a tcpdump in one of the servers that doesn't work, and the packet arrives and is returned by the server, but doesn't arrive in the machine behind the router. I dont know where im missing in the router configuration. The IP address that im trying to reach from inside to outside is 192.168.0.1. Here it goes the running config.
In show ip nat translations it appears the dynamic nat that it builds.
Sorry for my poor english :).