Distribution preference for service IP label aliases

A distribution preference for service IP label aliases is a network-wide attribute used to control the placement of the service IP label aliases on the physical network interface cards on the nodes in the cluster.

Configuring a distribution preference for service IP label aliases does the following:

• Lets you customize the load balancing for service IP labels in the cluster.
• Enables PowerHA SystemMirror to redistribute the alias service IP labels according to the preference you specify.
• Allows you to configure the type of distribution preference suitable for the VPN firewall external connectivity requirements.
• The distribution preference is exercised as long as there are acceptable network interfaces available. PowerHA SystemMirror always keeps service IP labels active, even if the preference cannot be satisfied.

Rules for the distribution preference for service IP label aliases

The following rules apply to the distribution preference:

• If you do not specify any preference, PowerHA SystemMirror by default distributes all service IP label aliases across all available boot interfaces on a network using the IPAT via IP Aliasing function. For more information on how the default method for service IP label distribution works, see Resource group behavior during cluster events.
• If there are insufficient network interface cards available to satisfy the preference that you have specified, PowerHA SystemMirror allocates service IP label aliases to an active network interface card that may be hosting other IP labels.
• You can change the IP labels distribution preference dynamically: The new selection becomes active during subsequent cluster events. (PowerHA SystemMirror does not require the currently active service IP labels to conform to the newly changed preference.)
• If you did not configure persistent labels, PowerHA SystemMirror lets you select the Collocation with Persistent and Anti-Collocation with Persistent distribution preferences, but it issues a warning and uses the regular collocation or anti-collocation preferences by default.
• When a service IP label fails and another one is available on the same node, PowerHA SystemMirror recovers the service IP label aliases by moving them to another NIC on the same node. During this event, the distribution preference that you specified remains in effect.
• You can view the distribution preference per network using the cltopinfo or the cllsnw commands.