[cisco-voip] Voice Mail down during AAR

[Robin H]

I have enabled AAR and it works fine, but when the remote user is not
answering the call, the caller got engage tone after ring timeout. I
have configured following items:

- set External Number Mask on IP Phones (both central and remote
sites), and voicemail ports
- set "Use Calling Party's External Phone Number Mask on all route patterns
- set RDNIS outgoing on remote gateway and RDNIS incoming at central gateway
- set AAR CSS on both central and remote site gateways/ip phones, and
also voicemail ports
- AAR Group: A -> B = prefix 91, B -> A = prefix 91
- Apply AAR Group on central and remote site phone DNs, and also
voicemail port DNs

Is there any other parameters that I miss out? Thanks