I have a replica set of 3 instances of mongod across 3 physically separate servers, all connected on a private network and running RHEL 7. When I create the replicaSet, then add the first additional member, everything is fine. Then I add the 3rd member, and almost immediately after successfully adding to the replicaSet, I get this HostUnreachable Loop. It always happens with the same server as well.

I've tried uninstalling and reinstalling mongo on all 3 servers, and rebooting. I've tried deleting the local databases on all 3. Nothing seems to work. I hope this is just something I've doing wrong so that the fix is quick and easy.

This is the error message on loop:

2016-06-14T23:21:06.435-0500 I REPL [ReplicationExecutor] Error in heartbeat request to request:27017; HostUnreachable: No route to host