- Cisco Unified Communications Manager -CUCM
- Exchange 2013 Unified Messaging
- Cisco Phone 1 – Common Area Phone No Voicemail Enabled
- Cisco Phone 2 – User Extension Voicemail Enabled
When are user presses the voicemail button on Cisco Phone 1 it connects to Outlook Voice Access (OVA) and prompts “To connect to your mailbox enter your extension” to check voicemail, when you enter the extension there is a quick ringing and then you hear “To connect to your mailbox enter your extension” again and keep looping.
However when you perform press the Voicemail button Cisco Phone 2 it recognizes the user and says their name , pressing the * key allows me to reach the “To connect to your mailbox enter your extension” I then enter another extension and it accepts extension and prompts to enter the PIN.
We ran some tracing on the CUCM and we found that in the INVITE the REFERRED-BY information Extension entered by caller is provided by the Exchange UM 2013 server
REFERRED-BY header REFERRED-BY: <sip:domain.com-ex01.domain.com;v=1.0;extension=5551212;c=ms-ova-data>
The CUCM fails to use the REFERRED-BY extension in the INVITE that is sent to the Exchange 2013 UM server and then it prompts you to enter the extension again.
The guys working on the CUCM found the below articles, one is not necessarily our issue but we decided to try it out.
CUCM ignores REFERRED-BY, due a design limitation, we have an enhancement bug open for it which is CSCtf35144 (https://tools.cisco.com/bugsearch/bug/CSCtf35144/?reffering_site=dumpcr), since CUCM SIP trunk does not support RFC3515 completely, supporting incoming REFERs (both in-dialog and out of dialog) and we use only Refer-To and Replaces header in the incoming REFER message (to route the call), however not supporting Referred-By Header. This has been fixed on CUCM 11.0 version
Here are the steps we performed in order to resolve the issue:
- First the CUCM was upgraded 10.5(2.12900) to 10.5(2.13900.12) <– This release fixes the issue when MTP is not enabled and set as best effort, it appears that it is fixed in version 11.0 when MTP is enabled but it has not been validated.
- On both the SIP Trunks for Exchange UM CAS and MBX
- Select Device –> Device settings –> SIP Profile
- Early offer support for voice and video calls* is set to: Best Effort (no MTP inserted), Click Save
Now from Cisco Phone 1 we dialed the Exchange UM Pilot number and entered the extension it now used the REFERRED-BY field in the current format and we were prompted to enter the PIN number.