Exchange - use all domain controller servers

Question

We have an environment with 3 domain controllers (let’s call them DC1, DC2 and DC3). DC1 and DC2 are Windows 2008r2, DC3 is a Windows 2016.

Lately I realized that my Exchange 2010 doesn’t work when I shutdown DC1, telling me “Exchange Autodiscover – Could not find any available Domain Conroller”. I checked the properties of the server in Exchange Management Console – Server Configuration and realized that only DC1 is listed in the System Settings as “Domain controller servers being used by Exchange”.

How can I make Exchange use the other domain controllers as well?

Solution 1

What you are seeing is the expected behaviour unfortunately.

Exchange will only use one domain controller and when that DC goes away, it doesn't look for another one for a period of time. Microsoft claim it is 15 minutes, but I find it is closer to 35 minutes. You can speed things up by restarting the System Attendant service. That forces Exchange to look for another domain controller immediately.

If you don't want to restart services, then configure a static DC at least two hours before the DC it is using is going away so that Exchange picks up the change. Remember to put it back to dynamic afterwards, as running Exchange permanently with static DCs is not best practise and can often cause problems later on (people forget it is set, and then take away the DC and wonder why Exchange falls over).

You should find an event log entry with the other domain controllers listed - so it does know about them.

Solution 2

You can configure multiple DCs as explained here (step 9):

to set the StaticDomainControllers:

Set-ExchangeServer -Identity -StaticDomainControllers DC-01.dc.local,DC-02.dc.local

Microsoft mentioned it here as:

The StaticDomainControllers parameter specifies whether to configure a list of domain controllers to be used by the server via DSAccess.

to set the StaticGlobalCatalogs:

Set-ExchangeServer -Identity -StaticGlobalCatalogs DC-01.dc.local,DC-02.dc.local

Microsoft mentioned it here as:

The StaticGlobalCatalogs parameter specifies whether to configure a list of global catalogs to be used by the server via DSAccess.

Comments

[Sembee]

Running Exchange with static domain controllers isn't best practise. Furthermore in my experience, while you can set multiple static DCs it doesn't actually resolve the problem - Exchange will only use one DC and it will not give up using that DC easily.