Hi Paul, There is no way for ser to know whether the old phone is updating from a new IP or if a second phone is trying to register. The second attempt will receive an error message with something like "max contacts has been reached" if I recall correctly. Dependent on the register interval you use for your UAs this is probably not an issue (unless the interval is long). We had a discussion on the list a while back on what would be appropriate register expiry times. I think it was Jan Janak who suggested 10 minutes as a compromise between load reduction and NAT restart (as the NAT may give the phone behind NAT a new port number) and other contact-related issues. g-) Java Rockx wrote: