The customer has one cluster callmanager deployed with two callmanager servers over the WAN. However, there is only one unity server(UM) installed at head office. On remote site where has one subscriber and voice gateway installed, all the inbound calls are going to unity AA and transferred to extensions of remote site(no DIDs). It also has SRST configured on this voice gateway.
For this deployment, we have the problems for the inbound calls during WAN outage but subscriber callmanager server still up: all the inbound calls will get fast busy because the subscriber callmanager can not reach the Unity server for AA and the SRST is not kicked in because all the remote site phones are still registered to the subscriber callmanager.
We tried to find a good solution for this scenario during wan down but subscriber up, we know that shutdown the subscriber at remote site is one of the solutions for SRST to work. But during wan outage, to access subscriber server from head office is also hard.
Can someone suggest any kind of solutions?