Multiple IdM domains/realms on the same subnet

Hey guys,

Currently I have one IdM domain (lets call it abc.com) on our subnet that services all of our Linux workstations.
For testing purposes I was thinking about setting up a second IdM domain (lets call this one xyz.com) on the same subnet.

I want the 2 domains to communicate with each other but I don't want any replication or exchanging of the data. The main thing that would be need to be accessible is user accounts and groups.

Has anyone tried this before with IdM? Any issues that came up?

Thanks,

Matt