So here is the situation: I have a polycom phone with extension 101@pbxAand 101@pbxB. Someone else has a polycom phone with extension 102@pbxAand 102@pbxB. If I try to call from 101@Bto 102@B, the phone rings, but as soon as 102 answers, the call hangs up immediately. If I change 102@B to 103@B, so that the extensions are now 102@A and 103@Bon the second phone, then phone calls from the second phone to the first work, but not the other way around. If I repeat the change on the first phone, so that it now has 101@A and 104@B, then calls work correctly in both directions. So, it seems as though if you have more than one registration but use the same extension on each, the polycom has issues with the RTP piece of the call. The SIP piece seems to work ok because the call actually makes it to the other phone and rings, but as soon as you pickup (when RTP should start) the call ends. Has anyone run into anything close to this before? I am sure my description is confusing and it's much easier to explain on a whiteboard, but hopefully it makes sense. Just to clarify, the two PBXs are not related to each other. I'm not trying to call from pbxA to pbxB. Carlos