Availability Prerequisites

Before you configure availability, you must do the following:

• Choose the primary and secondary controllers.
• Verify the network accessibility for the UDP connection between the two controllers. The availability link is established as a UDP session on port 13911.
• Set up a DHCP (Dynamic Host Configuration Protocol) server for AP subnets to support Option 78 for SLP, so that it points to the IP addresses of the physical interfaces on both the controllers.
• Ensure that the Poll Timeout value on the AP Properties tab Advanced dialog is set to 1.5 to 2 times of Detect link failure value on the Controller > Availability screen. For more information, see AP Properties Tab - Advanced Settings.

  If the Poll Timeout value is more than 1.5 to 2 times of Detect link failure value, the APs failover will be unnecessarily delayed, because the APs will continue polling the primary controller even though the secondary controller is ready to accept them as the failover APs.

• To achieve ideal availability behavior, set the Poll Timeout value for all APs to 15 seconds, and the Detect link failure on the Controller > Availability screen to 10 seconds.