vCenter appliance upgrade 5.1 -> 5.5

Hi,

I experimented with the upgrade from vShere 5.1 -> 5.5 in our somewhat limited lab environment.

One question remaining after basic testing is: 

If I upgrade the appliance, will the new one take on the old ones identity? In lab I was happy to

use DHCP for IP allocation, and didn't bother w/ proper DNS names.

In prod we have a static IP and a DNS entry for the appliance. What will happen to those during

the upgrade?  In lab (w/ the aforementioned parameters) the new appliance had an IP of its own,

which is not desirable in prod.

Cheers