One of the biggest challenges with HA over the WAN is the "split master syndrome" where each UCCX server believes the other to have failed when they loose connectivity with each other during a WAN outage.
In this case each UCCX server beleives it is the primary or master UCCX server and both go into service. Once WAN connectivity is restored they have no mechanism in place to resync their data correctly
Andy, if you lose Heartbeats to the Unified Call Manager on the master, the slave might not kick in in doubt if there is or not a master in service and do a master reelectioninstead causing the call in progress to be lost while it is busy doing so.
I could assure you it is unfortunately still something quite common in the event of a WAN connection even with some of the most reliable ones.
Hypothetically speaking, what if one of the servers is shutdown prior to the high speed WAN link being restored. Assuming nobody cares about the "new" data/calls on the shutdown server, would it the HA cluster resume normal operations again safely?
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.