Hello. I've been unable to troubleshoot this issue myself and am hoping for some help with it. We have a test deployment of Lync Server 2013 with Exchange Server 2007. Both are updated to the latest SP/CU. I've set up the integration between them and most things, like voice mail, are working fine. Lync users can dial the auto attendant however they cannot then be transferred to another extension.

Specifically, if I dial the auto attendant and try to connect to another user by name, the Exchange server sends a SIP REFER to the Lync server but the Lync server then immediately sends a TCP reset (I'm watching the traffic in Wireshark). There is no SIP error message sent back, the connection itself is just reset. Using the Lync trace tools, the call does not show up at all. The SIP REFER message from Exchange contains the correct SIP URIs for the calling and destination user (sip:user@domain.lan) so it looks like Exchange is looking up the user and attempting to transfer the call correctly but then Lync is denying it for some reason. In Event Viewer on the Exchange server it says the request timed out.

All numbers in Lync are extensions in E.164 (with ;ext=xxxx), there are no DID numbers. The Exchange dial plan is set for 4 digit extensions and uses only the extension number, which should be normalized by Lync to the full E.164 number (this works when done from a Lync client). User's numbers are stored in AD as just the 4 digit extension.

I've tried playing with all three settings for REFER support under the Lync global trunk configuration but they don't seem to change anything. Since the call doesn't show up in the OCSTracer utility I'm stumped as there's no pointer to why Lync might be denying the call. The only reason I know Exchange is sending the REFER is because I'm looking at it in Wireshark, Lync doesn't acknowledge it at all.

• Edited by RKINET 7 hours 39 minutes ago Added detail