What causes the Configuration Domain Controller to change (Application Log Event ID 2095 msexchangeadaccess) on a mailbox server? We are using Exchange 2007 and this mailbox server is an active node in a cluster. The Configuration DC changes between 1 and 3 times a day lately. The mailbox server also has lots of Event ID 2115 LDAP warnings. We have also seen this on other mailbox servers in the cluster, though maybe not as frequently. We have had a few 30 minute outages over the course of several weeks for a particular database group, even after moving it to a different node, and I'm trying to rule this out as a cause. (We have a support call in to MS for the outage, but they want us to get rid of the LDAP warnings.) Is it normal for the Configuration DC to change, or might this represent a problem with connectivity? Also, the 2115 warnings are frequent, though sometimes will stop happening for several hours before happening every 5 minutes for several more hours or longer. It seems to me that this indicates some sort of problem. Anyone know if it's likely to be a connectivity issue, or something else? I appreciate any help.

It is explained here. I don’t think this behavior has changed from Exchange Server 2003 to Exchange Server 2007. http://support.microsoft.com/kb/250570 Microsoft Exchange System Attendant will choose a Configuration Domain Controller when it starts. That choice will be honored by DSAccess for up to 10 hours. In Exchange 2000 Server SP2 and later, the Microsoft Exchange System Attendant will choose the Configuration Domain Controller only on the first service start which occurs during setup or upgrade. DSAccess performs a full network redetection either when the Kerberos ticket times out (default period of 10 hours), any time a configuration change is made (new global catalogs or domain controllers are added to the topology), or if all global catalogs or domain controllers go down If the configuration domain controller used by DSAccess is or becomes unavailable, another configuration domain controller is chosen from the set of available domain controllers. Any change in the configuration domain controller is propagated to all the processes using DSAccess on the same computer. Jasjit Singh Dhindsa | ITIL v3 | IASA Foundation Certified | MCITP: EMA 2010/2007 | MCTS: MES 2010/2007, OCS 2007 | MCSA: M+S | MCSE: M+S

It is explained here. I don’t think this behavior has changed from Exchange Server 2003 to Exchange Server 2007. http://support.microsoft.com/kb/250570 Microsoft Exchange System Attendant will choose a Configuration Domain Controller when it starts. That choice will be honored by DSAccess for up to 10 hours. In Exchange 2000 Server SP2 and later, the Microsoft Exchange System Attendant will choose the Configuration Domain Controller only on the first service start which occurs during setup or upgrade. DSAccess performs a full network redetection either when the Kerberos ticket times out (default period of 10 hours), any time a configuration change is made (new global catalogs or domain controllers are added to the topology), or if all global catalogs or domain controllers go down If the configuration domain controller used by DSAccess is or becomes unavailable, another configuration domain controller is chosen from the set of available domain controllers. Any change in the configuration domain controller is propagated to all the processes using DSAccess on the same computer. Jasjit Singh Dhindsa | ITIL v3 | IASA Foundation Certified | MCITP: EMA 2010/2007 | MCTS: MES 2010/2007, OCS 2007 | MCSA: M+S | MCSE: M+S

Thanks for that link, it was quite helpful. The most important fact that I got out of the article is that the Configuration DC is only one of three catagories, and it sounds like the GC and domain controller are more important than the configuration DC. One thing that I'm finding confusing is "In Exchange 2000 Server SP2 and later, the Microsoft Exchange System Attendant will choose the Configuration Domain Controller only on the first service start which occurs during setup or upgrade." This makes it sound as though the Configuration DC for later versions of Exchange should never change unless there are problems detecting it. Am I correct? What I am seeing in the Application Log would seem to suggest this is true, since sometimes it doesn't change for over 24 hours and other times just after a few hours. (We are using the default Kerberos ticket time of 10 hours.) I think the most important thing is that I find out why the Event ID 2115 warnings are happening.