Sharing in-band registration across multiple hosts

I have a single node with multiple virtual hosts host1.domain.com, host2.domain.com, host3.domain.cod and have in-band registration successfully creating accounts, e.g. foo@host1.domain.com. The user account exists only on the host the in-band registration was connected to.

I'd like to have users able to migrate between the hosts; e.g. in-band registration on host1.domain.com and then disconnect and connect to host2.domain.com; currently I keep track in the client and do another in-band registration on the second host.

Is there, what is the configuration, that would allow all user accounts to be shared across hosts, instead of per host. In the previous example in-band registration for foor@domain.com and be able to login in to any of host1.domain.com, host2.domain.com.

Thanks,
Richard.