We recently experienced an outage where out secondary data center was unavailable.  During this outage (including loss of secondary DNS server) hosts at our primary site that had selected a routing path through a conditional forwarder using the secondary DNS server were unable to resolve addresses.

Does this sound familiar and if so anything I can do to fix it?  

I am relatively new to DNS administration here so any help is appreciated.

Hi Wood,

Since the secondary DNS server was unavailable, queries sent to it could not be resolved.

To solve the problem, we could modify the conditional forwarder to forward queries to the primary server of the zone.(Or other secondary zone)

Open DNS manager, expand Conditional Forwarders. Right click on the corresponding one and click Properties, then we could edit the server.

Here is the guide:
Assign a Conditional Forwarder for a Domain Name:
https://technet.microsoft.com/en-us/library/cc794735%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396

Besides, we could also create a secondary zone on local DNS server to resolve the queries of the zone.

Here is the guide
Add a Secondary Server for an Existing Zone
https://technet.microsoft.com/en-us/library/cc816814%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396

Best Regards,

Leo