Oracle WebLogic Server 11g Administration Handbook

Naming Cluster Instances

When you create a cluster, you must provide the location information for all Managed Servers and the Admin Server. You can use either DNS names or IP addresses for naming the servers. Each of the Managed Servers must have a unique listen address and listen port combination. If your cluster nodes are all on the same server, they can of course use the listen address, but you must assign a different listen port to each Managed Server. Oracle recommends that you use DNS names for production environments, as the firewalls may cause translation errors when you use IP addresses. You must use the ExternalDNSName attribute of a server instance to define its external DNS name if its internal and external DNS names aren't identical. ...