[Serusers] SER behind DNAT

Hi! I have the following scenario: UA1 ----> SER1+NAT ----> Internet <----DNAT ROUTER <---- SER2 <----UA2 Both SER1+NAT and SER2 have 2 network interfaces and work with mhomed=1. SER1 is on the same machine as the NAT, so SER1 listens on a public address. SER2 is behind a router doing full DNAT to it, so it doesn't directly listen in a public address. Communication works in both ways, regardless of who starts the call! This is the good thing. The bad thing is, that when UA1 hangs up, the BYE request is sent to the IP address of the outmost interface of SER2, which is behind the DNAT router. How do I make SER1 make the bye request go to the public interface of the router? I've tried changing the advertised_address and record_route_preset parameters, and haven't achieved success yet! Has anyone faced a similar problem, or can give me hand with this problem? Thanx a lot!!! Óscar