I have been using Grandstream GXP 2000 & 2010 pones internally no problem with Voip unlimited here in the UK and all has been excellent. However I have 2 x Grandstream GXP 2000 External Extensions, and these i can get connected and they work PERFECTLY for everything internal calls external calls incoming outgoing excellent UNTILL the ip address changes at the external site then they loose connection. Nothing in particular seems to re-connect them ( re-boot does nothing) jiggle some of the settings a bit and finally they will go again but only until the ip changes. I thought Stun was supposed to solve this sort of thing? Am i missing something? My set up: IPPBX has a static External ip address and and static internal ip address. I have set the Sip server and outbound proxy to this address in my external phones The external phones have a dynamic external ip address and a fixed internal ip address all ports are forwarded and as i say i will work perfectly until the ip changes. Any ideas!?