If running the management agent on a host with multiple network interfaces, the createdomain command may fail if not all network interfaces are on the same subnet:
hadbm:Error 22020: The management agents could not establish a domain, please check that the hosts can communicate with UDP multicast.
The management agents will (if not configured otherwise) use the "first" interface for UDP multicasts ("first" as defined by the result from java.net.NetworkInterface.getNetworkInterfaces()).
The best solution is to tell the management agent which subnet to use (set ma.server.mainternal.interfaces in the configuration file, e.g., ma.server.mainternal.interfaces=10.11.100.0). Alternatively one may configure the router between the subnets to route multicast packets (the management agent uses multicast address 126.96.36.199).
Before retrying with a new configuration of the management agents, you may have to clean up the management agent repository. Stop all agents in the domain, and delete all files and directories in the repository directory (identified by repository.dr.path in the management agent configuration file). This must be done on all hosts before restarting the agents with a new configuration file.