This version of ParaStation MPI uses the ParaStation MPI RDP protocol to exchange status information between the psid(8) daemons. Therefore, multicast functionality is no longer required. It is still possible to use multicasts, if requested.

To enable Multicast message exchange, edit parastation.conf and uncomment the

  # UseMCast

statement.

If Multicast is enabled, the ParaStation MPI daemons exchange status information using multicast messages. Thus, a Linux kernel supporting multicast on all nodes of the cluster is required. This is usually no problem, since all standard kernels from all common distribution are compiled with multicast support. If a customized kernel is used, multicast support must be enabled within the kernel configuration! In order to learn more about multicast take a look at the Multicast over TCP/IP HOWTO.

In addition, the hardware also has to support multicast packets. Since all modern Ethernet switches support multicast and the nodes of a cluster typically live in a private subnet, this should be not a problem. If the cluster nodes are connected by a gateway, it has to be configured appropriately to allow multicast packets to reach all nodes of the cluster from all nodes.

On nodes with more than one Ethernet interface, typically frontend or head nodes, or systems where the default route does not point to the private cluster subnet, a proper route for the multicast traffic must be setup. This is done by the command

  route add -net 224.0.0.0 netmask 240.0.0.0 dev ethX

where ethX should be replaced by the actual name of the interface connecting to all other nodes. In order to enable this route at system startup, a corresponding entry has to be added to /etc/route.conf or /etc/sysconfig/networks/routes, depending on the type of Linux distribution in use.