Sunday, May 2, 2010

Exchange Unified Messaging 2007 / 2010 Co-Existence

In a Unified Messaging co-existence scenario with Exchange 2007 and Exchange 2010 - the migration path is to configure Exchange 2010 as the next hop from the PBX. If a call comes in that is destined for an Exchange 2007 user, Exchange 2010 will redirect the PBX to establish a connection with the Exchange 2007 server.

Here is a basic flowchart of how this works:


Looking at the SIP trace in Netmon, Exchange 2010 is sending the PBX a "302 Moved Temporarily" message:


Notice that the Contact field (the field that tells the PBX which server to redirect the call to) is using the FQDN of the Exchange 2007 server and not the IP address.

If the PBX cannot resolve the Exchange 2007 server via DNS (or some kind of host file), your call will be dropped.