After that it should be a process of converting the other system to HMC
managed and 'discovering' it.
Let me try this for you.
I have an HMC managing two systems in one town (HMC01) and an HMC managing
one system in another town (HMC02). Right now, they are not redundant.
(They were before a big hardware move).
I put the 10.10.x.yyy for a fsp currently controlled by HMC01 into the
test network connectivity for HMC02. Ping passed.
Now on HMC02 I open up Systems Management, Servers and see the server
currently controlled by HMC02. I expand Connections and select Add
Managed System. Enter in the IP address, oh crap, what was my HMC
password? Of course it doesn't match the type written page of these type
of passwords... Let me try this one... Well, not rejecting it, but it's
stuck on a screen with Reference Code of "Connecting 0000-0004-0000003C"
for a long time. Occasionally the 0000 becomes 0002.