I have a UC540 that is integrated with Exchange 2010 for voicemail via SIP. Internal calls and calls across existing POTS lines forward to Exchange with no problem. Also have a SIP trunk to the PSTN. Inbound calls across the SIP trunk will not forward to Exchange - I get fast busy. I believe the problem is that the SIP trunk to exchange requires TCP as the transport while the inbound SIP trunk requires UDP. I can forward calls across SIP to Unity Express with no problem. Anyone run into this?
Brandon
