Failover for business continuity

[Ram]

I am trying to setup a remote cyrus-replica to a different geographical 
location for business continuity.

In case the main server goes down the users will get switched to the 
remote server by making a DNS change.
The only issue is DNS replication would take a long time so the switch 
is not instantaneous.
How would one make the switch instantaneous ? Moving the IP is not 
possible because the Remote server is on a different network


Thanks
Ram