Cisco 400-051: CCIE Collaboration Exam Question - RAS Message for Alias Address Resolution

Which RAS message is used between two gatekeepers to resolve an alias address?

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Which RAS message is used between two gatekeepers to resolve an alias address?



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A. B. C. D. E.


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.


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.

The answer to this question is D. LRQ.

In a Cisco Unified Communications environment, a gatekeeper is a device that controls access to the network resources and provides call admission control (CAC), address translation, and bandwidth management services. Gatekeepers use the Resource Allocation Protocol (RAS) to exchange information with other gatekeepers in the network.

One of the functions of a gatekeeper is to resolve alias addresses. An alias address is a name or number that represents a set of endpoints. For example, a company might have a set of IP phones that are assigned the alias address "1234." When a call is placed to "1234," the gatekeeper needs to know which specific IP phone to route the call to.

To resolve an alias address, the gatekeeper sends a Location Request (LRQ) message to another gatekeeper in the network. The LRQ message contains the alias address and asks the other gatekeeper to provide the IP address of the endpoint that corresponds to that alias.

The other gatekeeper responds with a Location Confirm (LCF) message, which contains the IP address of the endpoint. The requesting gatekeeper can then use this information to route the call to the correct endpoint.

In summary, the LRQ message is used between two gatekeepers to resolve an alias address in a Cisco Unified Communications network.