I_MPI_PORT_RANGE is equivalent to MPICH_PORT_RANGE and it is used for the Hydra Process Manager. I_MPI_PORT_RANGE was introduced recently, use MPICH_PORT_RANGE for legacy Intel MPI. At startup Hydra checks for the first available open port and uses it for Hydra connections to the head node (you can check this with I_MPI_HYDRA_DEBUG=enable). If I_MPI_PORT_RANGE (or MPICH_PORT_RANGE) is specified, Hydra will use only open ports from the specified range. But the launcher and fabric can use different ports. So ssh (port 22), Hydra (I_MPI_PORT_RANGE) and DAPL SCM (if used) can use different ports. We advise to open up ports from 30000-59999.