Cisco IOS Gatekeeper LRQ Resolution Process

B.

LRQThese messages are exchanged between gatekeepers and are used for inter-zone (remote zone) calls.

For example, gatekeeper A receives an ARQ from a local zone gateway requesting call admission for a remote zone device.

Gatekeeper A then sends an LRQ message to gatekeeper.

B.

Gatekeeper B replies to the LRQ message with either a Location Confirm (LCF) or Location Reject (LRJ) message, which depends on whether it is configured to admit or reject the inter- zone call request and whether the requested resource is registered.

When a Cisco IOS gatekeeper receives an LRQ (Location Request), it will attempt to resolve the destination address by performing the following steps:

1. Check to see if the LRQ reject-unknown-prefix flag is set: The reject-unknown-prefix flag is used to control whether the gatekeeper should reject LRQs that contain destination addresses with unknown prefixes. If this flag is set, the gatekeeper will reject the LRQ and send a Location Reject (LRJ) message back to the sender. If this flag is not set, the gatekeeper will proceed to the next step.

2. Check to see if the destination address matches the technology prefix: The gatekeeper will compare the destination address in the LRQ with the technology prefix configured on the gatekeeper. If the destination address matches the technology prefix, the gatekeeper will attempt to resolve the address by checking its own zone database. If the destination address does not match the technology prefix, the gatekeeper will proceed to the next step.

3. Check to see if the destination address matches the hop-off technology prefix: The hop-off technology prefix is the prefix configured on a gateway or endpoint that is used to route calls through the gatekeeper. The gatekeeper will compare the destination address in the LRQ with the hop-off technology prefix configured on the gateway or endpoint that sent the LRQ. If the destination address matches the hop-off technology prefix, the gatekeeper will attempt to resolve the address by checking its own zone database. If the destination address does not match the hop-off technology prefix, the gatekeeper will proceed to the next step.

4. Check to see if the destination address matches the remote zone prefix: The remote zone prefix is the prefix configured on a remote zone that is used to route calls through the gatekeeper. The gatekeeper will compare the destination address in the LRQ with the remote zone prefix configured on the remote zone. If the destination address matches the remote zone prefix, the gatekeeper will forward the LRQ to the remote zone and wait for a response. If the destination address does not match the remote zone prefix, the gatekeeper will proceed to the next step.

5. Check to see if the LRQ forward-queries flag is set: The forward-queries flag is used to control whether the gatekeeper should forward LRQs to other gatekeepers if it cannot resolve the destination address locally. If this flag is set, the gatekeeper will forward the LRQ to the next hop gatekeeper specified in its gatekeeper zone prefix list. If this flag is not set, the gatekeeper will reject the LRQ and send a Location Reject (LRJ) message back to the sender.

In summary, the gatekeeper will attempt to resolve the destination address in the LRQ by checking its own zone database, the hop-off technology prefix, and the remote zone prefix. If it cannot resolve the address locally, it may forward the LRQ to another gatekeeper if the forward-queries flag is set.