I have a nw6.5 and a gw6.5 server that are going to need the ip address changed to a new network, from 90.x.x.x to 192.168.x.x.

I'm apprehensive about changing the ip address on both units and rebooting (particularly the GW), so is it possible for me simply add the new network address as a secondary ip? That way i can slowly migrate the rest of the network over to 192.168.x.x, and clients can access them at either address? Does the GW complicate this? Or it is wisest to just bite the bullet and change the ip address.