There are two special issues regarding the network configuration to be used with Heartbeat. First of all, you must allocate a multicast address to use for communication within the cluster nodes.
Secondly, you need to allocate an extra IP address and hostname for each PVFS daemon. In the example that this document uses, we must allocate 4 extra IP addresses, along with 4 hostnames in DNS for those IP addresses. In this document, we will refer to these as ``virtual addresses'' or ``virtual hostnames''. Each active PVFS server will be configured to automatically bring up one of these virtual addresses to use for communication. If the node fails, then that IP address is migrated to another node so that clients will appear to communicate with the same server regardless of where it fails over to. It is important that you not use the primary IP address of each node for this purpose.
In the example in this document, we use 225.0.0.1 as the multicast address, node{1-5} as the normal node hostnames, virtual{1-4} as the virtual hostnames, and 192.168.0.{1-4} as the virtual addresses.
Note that the virtual addresses must be on the same subnet as the true IP addresses for the nodes.