Cisco Cisco Access Registrar 4.2 Especificaciones descargar pdf (Pagina 379)

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Cisco Wireless LAN Controller Configuration Guide

OL-13826-01

Chapter 7 Controlling Lightweight Access Points

Performing a Link Test

Using the CLI to Retrieve the Unique Device Identifier on Controllers and

Access Points

Enter these commands to retrieve the UDI on controllers and access points using the CLI:

• show inventory—Shows the UDI string of the controller. Information similar to the following

appears:

NAME: "Chassis" , DESCR: "Cisco Wireless Controller"

PID: WS-C3750G-24PS-W24, VID: V01, SN: FLS0952H00F

• show inventory ap ap_id—Shows the UDI string of the access point specified.

Performing a Link Test

A link test is used to determine the quality of the radio link between two devices. Two types of link-test

packets are transmitted during a link test: request and response. Any radio receiving a link-test request

packet fills in the appropriate fields and echoes the packet back to the sender with the response type set.

The radio link quality in the client-to-access point direction can differ from that in the access

point-to-client direction due to the asymmetrical distribution of transmit power and receive sensitivity

on both sides. Two types of link tests can be performed: a ping test and a CCX link test.

With the ping link test, the controller can test link quality only in the client-to-access point direction.

The RF parameters of the ping reply packets received by the access point are polled by the controller to

determine the client-to-access point link quality.

With the CCX link test, the controller can also test the link quality in the access point-to-client direction.

The controller issues link-test requests to the client, and the client records the RF parameters [received

signal strength indicator (RSSI), signal-to-noise ratio (SNR), etc.] of the received request packet in the

response packet. Both the link-test requestor and responder roles are implemented on the access point

and controller. Therefore, not only can the access point or controller initiate a link test to a CCX v4 or

v5 client, but a CCX v4 or v5 client can initiate a link test to the access point or controller.

The controller shows these link-quality metrics for CCX link tests in both directions (out: access point

to client; in: client to access point):

• Signal strength in the form of RSSI (minimum, maximum, and average)

• Signal quality in the form of SNR (minimum, maximum, and average)

• Total number of packets that are retried

• Maximum retry count for a single packet

• Number of lost packets

• Data rate of a successfully transmitted packet

The controller shows this metric regardless of direction:

• Link test request/reply round-trip time (minimum, maximum, and average)

The controller software supports CCX versions 1 through 5. CCX support is enabled automatically for

every WLAN on the controller and cannot be disabled. The controller stores the CCX version of the

client in its client database and uses it to limit the features for this client. If a client does not support

CCXv4 or v5, the controller performs a ping link test on the client. If a client supports CCXv4 or v5, the

controller performs a CCX link test on the client. If a client times out during a CCX link test, the

controller switches to the ping link test automatically. See the “Configuring Cisco Client Extensions”

section on page 6-35 for more information on CCX.

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