CUCM handling of REFERs for Exchange 2010/2007 UM Dial Plans

CUCM handling of REFERs for Ex2010UM/Ex2007UM Dial Plans

Below is an interesting situation that may occur as you head down your migration path from Exchange Unified Messaging 2007 to 2010. In case you didn’t already know a Exchange 2007 and 2010 UM server can be part of the same dial plan for the purposes of mailbox migration. When a call from CUCM hits the Exchange 2010 UM server it uses a REFFER to transfer the call to the Exchange 2007 server if the user hasn’t been migrated yet. This is a pretty simplistic description but I think you get the idea. This link fully describes the migration process from Exchange 2007 to 2010.

Thanks to Dave Howe for providing the following information.

ProblemCisco Unified Communications Manager (CUCM) does not handle REFER properly for Ex2010UM/Ex2007UM Dial Plans

(UM) Dial Plan is associated both Ex2010UM and Ex2007UM servers
(Cisco) SIP Trunk configured between CUCM and Ex2010UM server
(Cisco) Route Pattern for SA Pilot (70000) configured to use SIP Trunk

Caller dials 70000 (SA Pilot Number)
-Call is placed from an unrecognized number (PSTN, conference room, etc)
-Caller has Exchange 2007 mailbox and is enabled for Unified Messaging
Ex2010UM server does not recognize caller, answers and prompts for extension
Caller enters extension, mailbox resolves to Exchange 2007 server
Ex2010UM server sends REFER to CUCM to transfer the caller to Ex2007UM server
CUCM responds with 202 Accepted, followed by two NOTIFY packets with 404 Not Found (transfer fails)
Ex2010UM cannot handle call, disconnects after telling caller that mailbox version is unsupported

Issue #1
DNS resolution failure
REFER-TO header sent from Ex2010UM contains FQDN of Ex2007UM server
CUCM must be able to resolve FQDN of Ex2007UM server to routable IP address

Issue #2
FQDN of Ex2007UM server sent in REFER-TO header is not defined as a routing target within CUCM
Route Pattern is used to route calls placed to extension 70000 to the IP address of Ex2010UM server
SIP Route Pattern containing FQDN of Ex2007UM server is required
In CUCM Administration UI:
1. Go to Call Routing > SIP Route Pattern > Add New
2. Select Domain Routing, enter the FQDN of the Ex2007UM server, then select the Ex2010UM trunk
3. Select the correct Route Partition, then click Save

Issue #3
INVITE from referred calls handled by CUCM do not contain REFERRED-BY information
Extension entered by caller is provided by Ex2010UM server in REFERRED-BY header
CUCM fails to use the REFERRED-BY extension in the INVITE that is sent to the Ex2007UM server
Caller hears, “Welcome, you are connected ….” and is prompted to enter their extension a second time
No workaround, contact Cisco (UM Product Group has a ticket open with them)


  1. Does the INVITE sent to Ex2007UM server contains the REFERRED-BY: header or does CUCM removes that header ?

  2. Great Post! We've been dealing with this exact issue and adding the SIP Route Patterns for our Exchange 2007 servers fixed the routing issue. Now I'm following up with Cisco to see if they have a workaround for handling the REFERRED-BY EXTENSION issue so our users don't have to deal with (2) SA menu's to get to their mailboxes.

    Thanks again, Brent

  3. This was a great bit of information. I had to change one part. In issue #2 on item 2 you say to point to the Exchange2010 trunk but in our case that is the trunk initally contacting Exchange so we had to enter the Exchagne2007 trunk. Which is where the call is being referred to. It got me 98% of what I needed. Thanks for posting the answer.

    Thanks, Rick P. University of Kentucky

  4. Can somebody tell me how this scenario would work between Exchange 2007 and Exchange 2010 in separate forests? I am in the process of migrating 2007 UM users to 2010 in a different forest and I can only use 1 pilot # for voice mail. Can referrals still work in this case?

  5. What a great post . This was a great bit of information.
    Call Handling

  6. I wanted to know about SIP Trunk in UK which can simplifies the network and also improves the communication level by reducing the connectivity charges. Can anyone suggest me something?


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