Have a domain with two hosts, where you basically clone the one configuration to the other host and then have the DC property point to the first one. Do not modify the <host name="local" > settings in host.xml (most users will just forget this).
Then start this "slave".

DC will print:
[Host Controller] 14:21:33,442 INFO [org.jboss.domain] (pool-1-thread-18) register host local

navigate to http://domain-controller:9990/domain-api/?json.pretty=true

This hangs and the DC logs shows exceptions about "network unreachable".

So allowing to register two hosts with the same name should not be allowed.