Hi Jonathon, Since the binary name is "mpich-ofi-gnu9-ohpc-3.4.2-3.1.ohpc.2.4.x86_64", I assume it is mpich -3.4.2 configured with ch4:ofi. We no longer use mpich2 to refer to the project, just mpich. With ch4:ofi, try setting the following environment variables: FI_PROVIDER=tcp FI_TCP_IFACE=eth0 That assumes you want to use the tcp provider and the private interface is eth0. There are other providers that you may choose and the iface selection variables will be different. You can set MPIR_CVAR_DEBUG_SUMMARY=1 to show the list of providers mpich probes during init. Best wishes, -- Hui ________________________________ From: Jonathon Anderson via discuss <[email protected]> Sent: Thursday, June 30, 2022 10:49 PM To: [email protected] <[email protected]> Cc: Jonathon Anderson <[email protected]> Subject: Re: [mpich-discuss] How to specify which Ethernet / IP interface to use? I'm trying to use mpich2 [1] on a cluster of compute nodes each of which has two Ethernet interfaces: one, an encumbered public / Internet interface, and another a private / intranet interface. mpich is defaulting to trying to use the public interface, which then hangs indefinitely with both nodes in my job stuck listening via UDP. I experience the same behavior whether I use mpiexec or srun --mpi=pmi2. How do I tell mpich which interface to use? Thanks! ~jonathon [1]: mpich-ofi-gnu9-ohpc-3.4.2-3.1.ohpc.2.4.x86_64 _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss