[c-nsp] Nat Issues With cisco Routers

[Lin]

Hi Everyone,

I am using a Cisco 1841 router, and behind the router are Polycom IP phones 
with private ips.  When nat is enabled, most of the phones register just 
fine. However, a few fail to register. The SBC on the Telco end responds 
with an "482 Loop Detected". It appears the Cisco router is sending the sip 
registeration request with a the public_ip:port that has already been 
registered with the SBC! Apparently the same port, on the same public ip, is 
being mapped to more than one device on the local network.  How the hell is 
this possible? Anybody ever encountered this before?

I tried to do a "no ip nat service sip tcp port 5060" command. This removes 
the "482 Loop Detected Error" and allows the client ip phone to register. 
However, outgoing calls fail, because the SBC on the other end responds with 
an "403" error. Apparently, the header being submitted is not acceptable.

Anybody come accros this before?


Lin