Business Continuity Plan -- How can I connect to DR Server if PROD site is completely Down
If you have:


2 Datacenters
1 Server in Each DC
Using SQL Server AlwaysOn Availability Groups


Then the following happens:


The Primary Datacenter Goes Down, Completely


How do you continue business continuity?

Assuming that the Availability Replicas are both set to Synchronous...


Quorum will have most likely been lost - you'll need to force quorum on the server in the DC that is still up. This can be completed a variety of ways. Powershell: Start-ClusterNode -FixQuorum , services: net start clussvc /fq , etc.
Connect to SQL Server now that the cluster was forced quorum. Failover the Availability Group. This will bring the listener with it. Whether Synchronous or Asynchronous is set, this can be accomplished by executing ALTER VAILABILITY GROUP [Name] FORCE_FAILOVER_ALLOW_DATA_LOSS
Test connectivity.


Depending on the settings of the listener in the windows cluster, your clients may need to flush their dns cache (to pickup the new ip if they are legacy clients).

Once the first DC comes back online we'll want to make sure to reconfigure and re-evaluate the situation.

Resources that will help you:


https://msdn.microsoft.com/en-us/library/hh781257.aspx (Solutions guide for HA/DR)
https://msdn.microsoft.com/en-us/library/dn425173.aspx (MSIT case study for HA/DR)