Gentlemen, If I was using SER as a proxy server to deal with clients behind NATs, I can understand the concept - the sip proxy rewrites the header information to correct for the NATed client. Where I have a large "hole" in my understanding is concerning inbound calls from PSTN. Currently, these arrive at our Asterisk box which has no knowledge of the clever things SER should be doing to deal with the NATed clients. Can anyone please fill in the gaps in my understanding ? Better still.....can anyone let me have a look at their Asterisk and SER config files on a system that works ??? Jim -- --- www.yakara.com