The VIP will be assigned to Master only. Whenever the failover or switchover will happen EFM will take care of the VIP assignment to the new master.
For each EFM cluster (that includes Master, slave, and witness) there will be one VIP and for another cluster, there should be another VIP.
What about the VIP,can i assing one vip for both instance or one instance one VIP.
Which one is advisable.if failover happen how will VIP will react and swithcing(promotions).
I would think you'd need a separate vip for each cluster. That way if there's a failover or switchover in one it doesn't affect the vip of the other. I hope I understood the question correctly.