User`s manual

H.323 User's Manual 8. Telephony Capabilities
Version 5.0 263 December 2006
8.4 Redundant Gatekeeper Implementation
The redundant Gatekeeper mechanism (IsRedundantGKUsed=1), similar to the Alternate
Gatekeeper procedure (described in para. 7.2.6 in the H.323 standard), provides Mediant
1000 gateways with Gatekeeper redundancy options. This mechanism allows the gateway
to use up to two additional Gatekeepers as a backup in the event of a primary Gatekeeper
failure.
The redundant Gatekeeper mechanism is identical to the Alternate Gatekeeper mechanism
with the exceptions that all Alternate Gatekeeper fields in RAS messages are ignored, and
the IP addresses of the two redundant Gatekeepers are provided by the user (via the
Embedded Web Server or the ini file) and not by the primary Gatekeeper.
When Gatekeeper redundancy is enabled, if there is no response from the primary
Gatekeeper or if a registration request is rejected by the Gatekeeper (RRJ), the gateway
tries to communicate with one of the two redundant Gatekeepers. When a redundant
Gatekeeper is found, the gateway registers with it and continue working with it until the
next failure occurs (current Gatekeeper is not responding). If none of the Gatekeepers
respond, the gateway goes over the list again and works with the first responsive
Gatekeeper.
The Mediant 1000 gateway can fallback to the internal ‘Tel to IP Routing’ table when
communication with Gatekeepers is lost. If this option is enabled (IsFallbackUsed=1), the
Mediant 1000 starts using its internal routing table, and works without a Gatekeeper. The
Mediant 1000 continues scanning for an active Gatekeeper. When such Gatekeeper is
found, the gateway switches from internal routing back to Gatekeeper routing.
To enable redundant Gatekeepers set the following parameters in the ini file:
 IsGatekeeperUsed = 1
 IsRedundantGKUsed = 1
 GatekeeperIP = IP address of the primary Gatekeeper
 GatekeeperIP = IP address of the first redundant Gatekeeper
 GatekeeperIP = IP address of the second redundant Gatekeeper
Note: Users can use the Alternate Gatekeeper mechanism (AlternativeGKUsed)
described in para. 7.2.6 in the H.323 standard instead of the redundant
Gatekeeper mechanism. The Alternative and Redundant mechanisms
mustn’t be used simultaneously.