Cisco IOS Gatekeeper: Resolving Destination Address | Exam 400-051

Cisco IOS Gatekeeper: Resolving Destination Address

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Question

When a Cisco IOS gatekeeper receives an ARQ from a registered endpoint, what is the first step it will take in an attempt to resolve the destination address?

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Explanations

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A. B. C. D. E.

B.

Admission Request (ARQ) and Location Request (LRQ) are the two H.225 Registration, Admission, Status (RAS) messages that trigger a gatekeeper to initiate the call routing decision process.

-> ARQLocal zone messages that are sent by H.323 endpoints (usually gateways) to the Cisco gatekeeper.

Gatekeepers receive ARQs from an endpoint if.

- A local zone endpoint initiates a call.

OR - A local zone endpoint request permission to admit an incoming call.

When a Cisco IOS gatekeeper receives an Admission Request (ARQ) from a registered endpoint, it will perform several steps to resolve the destination address. The first step it takes depends on the configuration of the gatekeeper and the type of call being made.

The possible steps that the gatekeeper can take to resolve the destination address are:

A. Check to see if the destination address is locally registered: The gatekeeper checks if the destination address is registered with it locally. If the address is found to be registered, the gatekeeper sends an Admission Confirm (ACF) message to the calling endpoint, which contains the address of the destination endpoint.

B. Check to see if the destination address matches the technology prefix: The gatekeeper checks if the destination address matches the technology prefix. This prefix is typically configured on the gatekeeper and indicates the type of call being made. If the destination address matches the technology prefix, the gatekeeper sends an ARJ (Admission Reject) message to the calling endpoint, indicating that the call cannot be completed.

C. Check to see if the destination address matches the local zone prefix: The gatekeeper checks if the destination address matches the local zone prefix. This prefix is configured on the gatekeeper and is used to group endpoints based on their location or other criteria. If the destination address matches the local zone prefix, the gatekeeper forwards the ARQ message to the gatekeeper responsible for the destination endpoint.

D. Check to see if the destination address matches the remote zone prefix: The gatekeeper checks if the destination address matches the remote zone prefix. This prefix is configured on the gatekeeper responsible for the destination endpoint and is used to group endpoints based on their location or other criteria. If the destination address matches the remote zone prefix, the gatekeeper sends a location request to the remote gatekeeper, asking for the address of the destination endpoint.

E. Check to see if the destination address matches the default technology prefix: If none of the above steps resolve the destination address, the gatekeeper checks if the destination address matches the default technology prefix. If it matches, the gatekeeper sends an ARJ message to the calling endpoint, indicating that the call cannot be completed.

In summary, when a Cisco IOS gatekeeper receives an ARQ from a registered endpoint, it will first check if the destination address is locally registered. If not, it will go through a series of steps to resolve the address, including checking the technology prefix, local zone prefix, remote zone prefix, and default technology prefix.