I've installed multisite (subdirectories) at emphasysrealty.com.
Using WP Multi Network, I created a second network at wpbroker.com.
Then via WordPress MU Domain Mapping, I mapped to wpbroker.com. (At first I wasn't sure this was necessary because wpbroker.com already displayed the front end of my site as expected, but pages such as /about/ wouldn't display until I set up domain mapping. Later, though, I deactivated domain mapping, and I'm still able to get to pages such as /about/. Not sure what's up with that.)
Next I created a child site at wpbroker.com/agentred/, but I can't view or access it. When I click the Backend link, I'm redirected to the backend for wpbroker.com. When I try to go to the front end, I get a 404 because it thinks I'm looking for a page on wpbroker.com vs an actual child site.
Any suggestions as to what I should change?