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Unity issue with partner GC

Hello all,

My environment is Unity 5.0(1) partnered to Exchange 2010 (with a pair of CAS servers using Windows load balancing, and a DAG pair of mailbox servers) and AD is hosted by a primary and secondary DC.

My problem is that Unity is 'dropping' to UMR mode sometime after my DCs reboot (this has been a recurring problem for some time). After a previous TAC case, I set the two DCs to reboot at different times (2 hours apart), but the problem is still occurring. In fact, this last time it occurred nearly 5 hours after the reboot (which only takes about 15 mins tops). I think I've narrowed down the 'source error' to this:

Event Type: Warning
Event Source: CiscoUnity_MALEx
Event Category: Warning
Event ID: 30019
Date: 6/20/2012
Time: 1:48:06 AM
User: N/A
Computer: TAWK3UNITY01
The MAPI subsystem has indicated that the Global Catalog Server

<Primary domain controller> which is used to resolve addresses for message submission cannot be reached, and that it has switched to using Global Catalog server <Exchange NLB hostname>. Unity will continue to function using this newly selected Global Catalog server and will not automatically switch back to the original one. If Unity does not have a dedicated connection with sufficient bandwidth to the newly selected server, then there may be significant delays in Exchange access by Unity. Please verify that Unity has a good connection to the new Global Catalog for proper functioning.

My question is, where is the MALEx service getting its GC list, because the GC it's switching to is the NLB virtual hostname of my Exchange CAS servers, which has no GC roles at all, instead of my secondary DC?

I managed to correct the problem after reading this article:

and setting the partner GC back to a valid GC via the '001e6602' registry key, then restarting the Unity services. FYI, before I was correcting the issue by rerunning the Message Store Configuration Wizard to rehome Unity to Exchange.

Any help you could provide or light you might shed on this situation will be greatly appreciated, and thank you in advance!

Luke Whittall

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