Availability

The Extreme Networks ExtremeWireless Software system provides the availability feature to maintain service availability in the event of a controller outage.

Note

During the failover event, the maximum number of failover APs the secondary controller can accommodate is equal to the maximum number of APs supported by the hardware platform.

Wireless APs that attempt to connect to the secondary controller during a failover event are assigned to the WLAN (Wireless Local Area Network) Service that is defined in the system‘s default AP configuration, provided the administrator has not assigned the failover APs to one or more VNSs. If a system default AP configuration does not exist for the controller (and the administrator has not assigned the failover APs to any WLAN Service), the APs will not be assigned to any WLAN Service during the failover.

A controller will not accept a connection by a foreign AP if the controller believes its availability partner controller is in service. Also, the default AP configuration assignment is only applicable to new APs that failover to the backup controller. Any AP that has previously failed over and is already known to the backup system will receive the configuration already present on that system. For more information, see Configuring the Default Wireless AP Settings.

During the failover event when the AP connects to the secondary controller, the users are disassociated from the AP. Consequently, the users must log on again and be authenticated on the secondary controller before the wireless service is restored.

Note

If you want the mobile user‘s session to be maintained, you must use the ‘session availability‘ feature that enables the primary controller‘s APs to failover to the secondary controller fast enough to maintain the session availability (user session). For more information, see Session Availability.

The availability feature provides APs with a list of local active interfaces for the active controller as well as the active interfaces for the backup controller. The list is sorted by top-down priority.

If the connection with an active controller link is lost (poll failure), the AP automatically scans (pings) all addresses in its availability interface list. The AP then connects to the highest priority interface that responds to its probe.