High Availability with WebLogic Clusters - Oracle WebLogic Server 12c Advanced Administration - page 71

How it works...
All instances of the domain are now using the adminhost.domain.local hostname as the
Administration Server hostname.
The Administration Server should be started normally on the prod01 machine and listens for
the IP address bound to adminhost.domain.local , which points to an IP address on the
prod01 machine as well.
If the prod01 machine crashes, change the adminhost.domain.local IP address to the
prod02 machine or move the VIP to prod02 and start the Administration Server on prod02 .
This change can be made by setting up the DNS Server or by making
changes to the /etc/hosts file of the machines among a variety of
other options. Please contact your network administrators to change the IP
address of the adminhost.domain.local properly.
Follow the usual procedure to start the Administration Server, but now on prod02 machine.
As soon the Administration Server starts, all Managed Servers will reconnect automatically
to it looking for the adminhost.domain.local new location and new IP address.
In earlier versions, the DNS cache of the JDK didn't have a default
time-to-live (TTL), so a WebLogic Server instance didn't recognize that
a hostname had its IP address changed until restarting the instance.
To avoid the need of a restart, a JVM argument had to be added to
change the TTL.
In WebLogic 12 c (using JDK > 1.6), the JVM argument is not needed
anymore. Now the JDK sets a default DNS TTL to 30s.
There's more...
Update the start and stop scripts after changing the Administration Server's Listen
Address value.