Before configuration of availability, the following must be done:
1. Choose the primary and secondary controllers.
2. Verify the network accessibility for the UDP connection between the two controllers if firewall is present. The availability link is established as a UDP session on port 13911.
3. Set up a DHCP 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. Or add DNS entries for the controller. See articles in the Additional notes section.
4. 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 IdentiFi Wireless Appliance > Availability screen. For additional information, see “AP Properties Tab Configuration” on page 3‐39 of the User Guide. 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.
5. To achieve ideal availability behavior, you must set the AP Poll Timeout value for all APs to 15 seconds, and the Detect link failure on each IdentiFi Wireless Appliance Controller > Availability>Detect Link Failure to 10 seconds