Administrators use the Alternate Gatekeeper List (AGL) feature of Communication Manager to specify the number of IP interfaces for each connected network region that are allowed for telephones within a specific network region.

The AGL feature limits the number of entries in the AGL and is intended to simplify network region administration. This feature can improve system performance and reliability. It also reduces the time that it takes for telephones to failover to the Survivable Core or Survivable Remote Server.

This feature enhancement is available to all H.323 telephone types and does not require any Communication Manager license file feature activation or firmware upgrades.

The H.323 telephones use the AGL when they cannot reach or register with their primary gatekeeper. H.323 telephones use the AGL list of PE for recovery when the current PROCR is no longer available. The Survivable Remote Servers can be a separate failover set if the alternatives for reaching the main server are exhausted.

H.323 telephones can receive from the Communication Manager server an AGL with up to six Survivable Remote Servers and one survivable gateway. This is true whether or not the region of the telephone is using the Administrable AGL feature. Without AGL, the number of nonsurvivable IP interface addresses in the network region depends on several factors:

To use the Communication Manager AGL feature, administrators enter a numeric value in the AGL field of the Inter Network Region Connection Management screen. Use the Inter Network Region Connection Management screen to administer connections between a source network region and all other destination network regions. The entries administered in the AGL field within each source network region represent the number of PE that Communication Manager builds into each Alternate Gatekeeper List and sends to each H.323 telephone that is in that source network region. After entering the numeric values, Communication Manager calculates the total number of gatekeepers that are assigned to each destination region. The total AGL assignments for each region must add up to 16 or lower. If administrator enters a value that makes the AGL assignment greater than 16, the system displays an error message.

Communication Manager tracks each PE addresses sent in the AGL to each telephone.

For more information on the administration procedures for this feature, see Administrable Alternate Gatekeeper List administration.