I think I didn’t describe my situtation correctly. What I meant is that they are different systems. One has IP: a.b.c. d , and the other has IP: a.b.c. e .

I see. This should be fine. You only need to specify one of them as the master, and set MASTER_ADDR and MASTER_PORT for all peers to point to that master. This will allow all peers to do rendezvous, and the rendezvous process will create connections between pairs.