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4.5.3. Network Configuration

Clicking on the Network tab displays the Network Configuration page, which provides an interface for configuring the network transport type.
You can use this tab to select one of the following options:
  • UDP Multicast and Let Cluster Choose the Multicast Address
    This is the default setting. With this option selected, the Red Hat High Availability Add-On software creates a multicast address 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:
    • For IPv4 — The address formed is 239.192. plus the lower 16 bits generated by Red Hat High Availability Add-On software.
    • For IPv6 — The address formed is FF15:: plus the lower 16 bits generated by Red Hat High Availability Add-On software.


    The cluster ID is a unique identifier that cman generates for each cluster. To view the cluster ID, run the cman_tool status command on a cluster node.
  • UDP Multicast and Specify the Multicast Address Manually
    If you need to use a specific multicast address, select this option enter a multicast address into the Multicast Address text box.
    If you do 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 Conga, see Section 5.4, “Starting, Stopping, Restarting, and Deleting Clusters”.


    If you specify a multicast address, make sure that you check the configuration of routers that cluster packets pass through. Some routers may take a long time to learn addresses, seriously impacting cluster performance.
  • UDP Unicast (UDPU)
    As of the Red Hat Enterprise Linux 6.2 release, the nodes in a cluster can communicate with each other using the UDP Unicast transport mechanism. It is recommended, however, that you use IP multicasting for the cluster network. UDP Unicast is an alternative that can be used when IP multicasting is not available. For GFS2 deployments using UDP Unicast is not recommended.
Click Apply. When changing the transport type, a cluster restart is necessary for the changes to take effect.