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