I have set up an AlwaysOn with a primary and secondary replica on different subnets but I have been forced to use Registerallprovidersip set to 1. This causes the listener to only have 0 IP address in DNS which means I am at the mercy of DNS replication when a failover event occurs as it will take sometime for the listner's IP to update.
Has anyone in a similar situation found ways to improve failover time?