The Alternate Gatekeeper List (AGL) feature is available on Communication Manager 5.1 and later. Using the Alternate Gatekeeper List (AGL) feature, you can specify the number of IP interfaces for telephones connected within a specific network region.

The Administrable Alternate Gatekeeper List feature limits the number of entries in the AGL, and is intended to simplify network region administration. This feature improves system performance and reliability, and also reduces the time that it takes for telephones to failover to the Survivable Core Server (Enterprise Survivable Servers) or Survivable Remote Server (Local Survivable Processor).

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

The Alternate Gatekeeper List (AGL) is used by H.323 IP telephones when they cannot reach or register with their primary gatekeeper. The AGL is a list of C-LANs/PE used by H.323 IP telephones to recover to when the current C-LAN is no longer available. The Survivable Remote Server may be a separate failover set if the alternatives for reaching the main server are exhausted.

From Communication Manager 5.1 onwards, H.323 IP telephones in a network region can have an AGL list with no more than 16 members. You can continue to use the AGL feature of prior releases (up to 65 C-LAN/PE members in the AGL), or use the more efficient method of controlling telephone recovery by condensing the number of gatekeepers sent by Communication Manager based on new network region administration.

To use the Communication Manager AGL feature, administrators enter a numeric value in the new AGL field of the Inter Network Region Connection Management screen. The Inter Network Region Connection Management screen is used 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 C-LANS and/or PE that Communication Manager builds into each Alternate Gatekeeper List and sends to each IP (H.323) telephone that is in that source network region. Once the numeric values are entered, Communication Manager calculates the total number of gatekeepers that are assigned for each destination region. The total AGL assignments for each region must sum to 16 or lower. If an administrator enters a value that makes the AGL assignment greater than 16, the system displays an error message.

Communication Manager tracks each of the C-LAN/PE addresses sent in the AGL to each telephone. For example, a destination network region containing 20 C-LANs can be administered to have only 3 C-LANs from that region in each AGL. As a result, Communication Manager responds to each new registration request with an AGL constructed using the administered number of C-LANs for the region, and is independent of priority, socket load, and service state.

For more information on the administration procedures for this feature, see Administering Avaya Aura® Communication Manager.