VIP change on load balancer on 12.1 version.

Could you give us a more detailed description of your problem?

I need to replace the existing vip and assign a new vip in its place , so just wanted to know is there any precautions i have to take or do i have to change it from any other place excluding VS.

No precautions or other places. (or are you going to assign a new IP address, then you need to change the DNS)

If you don't want to interrupt client traffic, you could perform these actions on your standby BIG-IP and sync the configuration when your finished configuring the new virtual server. All active sessions to the old virtual server will stay in memory until the client ends his session.

Cheers,

Kees