That's an interesting hack for MPI, but I don't think it would be worth the complexity of implementing it. There are two possible use cases here: One: You're t

That's an interesting hack for MPI, but I don't think it would be worth the complexity of implementing it. There are two possible use cases here: One: You're testing multiple VMs on one box to simulate a network. This is a sane use case, but a bit of overhead from network latency isn't going to kill you. It definitely isn't worth the effort of messing around with faking your network. Two: You're trying to wring whatever performance you can out of a single box. In this case, you can ditch the VMs, and just run your MPI nodes as threads or processes on the local machine, using far faster and more efficient transports than TCP. Also, in this specific case, note that the instances are not necessarily on the same machine.