Per the SRND for CallManager:
In addition to the option of adding multiple clusters by adding additional integrations for each new
Unified CM cluster in Cisco Unity, Unified CM supports Annex M.1, Message Tunneling for QSIG,
which gives administrators the ability to enable QSIG on intercluster trunks (ICTs) between Unified CM
clusters. When QSIG is enabled on ICTs, Cisco Unity needs to integrate with only one Unified CM
cluster and designate ports only in this one cluster for turning MWIs on and off, even when supporting
multiple clusters. The Annex M.1 feature in Unified CM allows for propagation of the MWI requests
across the ICTs to the proper Unified CM cluster and phone within that cluster. All calls originating in
other clusters can be forwarded to the Unity server integrated to that one cluster. There is no need to
designate MWI ports on the other clusters when Annex M.1 is enabled on the ICT.
I have setup the ICT with QSig on two CallManager clusters. It is Unity version 4.2(1). The cluster that has Unity directly connected is version 4.2(3). The version on the other side of that QSig ICT is 6.0. I can dial numbers to and from either CallManager cluster without problem. I am finding that when calling a phone registered to the CallManager that is NOT directly connected to Unity that the redirecting number is not present and the call goes to the opening greeting via the CFB, CFNA, or CFA. Redirecting number is NOT an option when using QSig on the ICT. So how does this work? If I get rid of the QSig on the ICT and select the redirecting number it goes to the appropriate VM box everytime. Also, with the ICT using QSig MWI does not work when a message is left on a phone across the trunk.
Has anyone gotten this to work? Any tips would be great!