If you set up a secondary IP address on an interface - say int fa0/0 zone "inside" - does that immediately take effect for the traffic on that subnet? I will be working on a network where they installed too small a subnet on the inside and I'd like to ease the migration by putting on a secondary IP and let them renumber all their stuff etc. Then as final brief step I'll nuke the primary address and make the secondary primary.
Would this work? Thanks.