Ethernet is the default network card that STAR-CCM+ is configured to use, and is supported using the MPICH MPI library. In this case you need not add any specific MPI driver option to the command line. Since most cluster nodes are connected with an Ethernet network device the default option should work.
In some cluster configurations each node may be equipped with more than one network device. For example, a simple 100/10BaseT Ethernet device might be accompanied by a higher-speed Gigabit Ethernet device. Since both devices use the same underlying communication protocol (TCP/IP), the same MPI library can be used, but when two network devices are present using the same communication protocol it is often necessary to tell STAR-CCM+ explicitly which one to use. This is normally achieved by specifying the correct hostnames associated with each network device.
If you use the HP MPI library with Ethernet, polling is on by default. To avoid the performance degradation that polling can cause, you should ensure that all processes are allocated to unique CPUs when using these drivers.
To deactivate polling, use the following line command:
-mpidriver hp2:-polling=no
To activate it again:
-mpidriver hp2:-polling=yes