Ok, so i have 3cx installed working with a SPA-3102 as a gateway and an Engin SIP account. I have 2 phones, one is a Avaya desk phone (x500), the other is a Nokia E51 (x501) connected wirelessly as a SIP client. Incoming calls via both Voip and PSTN are routed through to both phones in a group - Works fine The E51 can call the Desk phone no problems but for some reason the desk phone can not call the E51 and i have no idea why. Log entries: Code: 09:30:42.095 [CM503008]: Call(231): Call is terminated 09:30:42.033 [CM503020]: Normal call termination. Reason: No answer 09:30:42.033 [CM503016]: Call(231): Attempt to reach "501"<sip:email@example.com> failed. Reason: No Answer 09:30:42.033 [CM503003]: Call(231): Call to sip:firstname.lastname@example.org has failed; Cause: 408 Request Timeout; internal 09:30:09.923 [CM503025]: Call(231): Calling Ext:Ext.501@[Dev:sip:email@example.com:5060;transport=UDP] 09:30:09.861 [CM503004]: Call(231): Route 1: Ext:Ext.501@[Dev:sip:firstname.lastname@example.org:5060;transport=UDP] 09:30:09.861 [CM503010]: Making route(s) to "501"<sip:email@example.com> 09:30:09.861 [CM505001]: Ext.500: Device info: Device Not Identified: User Agent not matched; Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent: [Avaya SIP R2.2 Endpoint Brcm Callctrl/126.96.36.199 MxSF/v188.8.131.52] PBX contact: [sip:firstname.lastname@example.org:5060] 09:30:09.861 [CM503001]: Call(231): Incoming call from Ext.500 to "501"<sip:email@example.com> Can somone explain this? One thing that might have something to do with it is in the initial setup, i set the extension range to start at 100. As it turns out, this was no good so i have manually changed the extensions to 500, 501 etc. I could not find a 'propper' way to change the start of the range other than to re-install the whole lot.