6.14.2. Multicast Configuration

If you do not specify a multicast address in the cluster configuration file, the Red Hat High Availability Add-On software creates one based on the cluster ID. It generates the lower 16 bits of the address and appends them to the upper portion of the address according to whether the IP protocol is IPv4 or IPv6:

You can manually specify a multicast address in the cluster configuration file with the following command:

ccs -h host --setmulticast multicastaddress

Note that this command resets all other properties that you can set with the --setmulticast option to their default values, as described in Section 6.1.5, “Commands that Overwrite Previous Settings”.

If you specify a multicast address, you should use the 239.192.x.x series (or FF15:: for IPv6) that cman uses. Otherwise, using a multicast address outside that range may cause unpredictable results. For example, using 224.0.0.x (which is "All hosts on the network") may not be routed correctly, or even routed at all by some hardware.

If you specify or modify a multicast address, you must restart the cluster for this to take effect. For information on starting and stopping a cluster with the ccs command, see Section 7.2, “Starting and Stopping a Cluster”.

To remove a multicast address from a configuration file, use the --setmulticast option of the ccs but do not specify a multicast address:

ccs -h host --setmulticast