The one-way audio issue is caused by the default transfer methods used by different software versions of Cisco CallManager Express and Cisco Unity Express (CUE).
CUE version 2.3.1 uses the semi-attendant method as the default transfer operation. Prior to version 2.3, CUE used the blind transfer or bye-also method. Cisco CallManager Express versions earlier than 3.4 use the blind (bye-also) transfer method.
Cisco CallManager Express version 4.0 and later use the semi-attendant transfer method. Therefore, CUE 2.3.1 is not backwards compatible to any Cisco CallManager release earlier than 3.4, unless the transfer method is changed back to blind (bye-also).
The issue is documented in Cisco bug ID CSCse31911.
To resolve this issue, perform one of these procedures:
- Change the Cisco IOS version on the Cisco CallManager Express to 12.4.4XC or later, so the transfer method is the same on the Cisco CallManager Express and CUE 2.3.1 systems.
- Change the transfer method on the CUE to blind bye-also to allow interworking between earlier versions of Cisco CallManager Express and CUE 2.3.1.
Change the CUE configuration under the ccn subsystem sip, and issue the transfer-mode blind bye-also command.
The configuration looks like this:
ccn subsystem sip
gateway address "10.66.75.55"
transfer-mode blind bye-also <_------ _="_" add="add" br="br" command="command" this="this"> end subsystem