Reroute Production server to Test Server

[Binubaby]

Hello

I have 2xHPUX 11.31 Database Oracle RAC systems on HP rx6600 in prouction -- SERVER-A

I want to take these servers for HW maintenace/upgrade for one full day

So I want to reroute network connection of production SERVER-A to another test system (SERVER-B) on the same subnet, So application users can access database from test server during this outage

Will it help through DNS entry ?

Please advise how to achive this in a proper way

Thank You

BB