Troubleshooting guide

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Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
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Chapter 7 Troubleshooting the CMTS
Troubleshooting the Cisco uBR7246VXR
Setting Frequency Threshold to Affect Power Adjustment
To control power adjustment methods by setting the frequency threshold, use the cable upstream
freq-adj averaging interface configuration command. To disable power adjustments, use the no form of
this command.
cable upstream n freq-adj averaging % of frequency adjustment
no cable upstream freq-adj averaging
Table 7-4 displays descriptions of the arguments in the cable upstream freq-adj averaging command.
The following example shows how to change the power adjustment method when the frequency
adjustment packet count reaches 50 percent:
router(config-if)# cable upstream 0 freq-adj averaging 50
Additional Diagnostic Commands
The commands described in the following are used in addition to the flap list commands to help you in
troubleshooting uBR and cable modem problems.
Pinging Unresponsive Cable Modems
Ping DOCSIS is allows you to quickly diagnose the health of a channel between the Cisco uBR7200
series universal broadband router and the cable modem. The technology uses 1/64—the bandwidth of IP
ping—and works with cable modems that don't have an IP address. This allows you to ping cable
modems that are unable to complete registration, have internal bugs, or that are unresponsive due to a
crash.
The Ping DOCSIS feature provides a real-time view and plot of requested power adjustments, as well as
a measure of optimal headend reception power. This gives you the ability to solicit a configured number
of periodic ranging requests from a cable modem.
To ping a specific cable modem to determine if it is online, use the following command (with a specific
MAC address) in privileged EXEC mode:
ping docsis addr
Table 7-4 Cable Upstream Power Adjust Syntax Descriptions
Syntax Valid Values
n Specifies the upstream port number.
averaging Specifies that a percentage of frequency adjustment packets is
required to change the adjustment method from the regular power
adjustment method to the noise power adjustment method.
% of frequency adjustment Specifies the percentage of frequency adjustment packets required to
switch from the regular power adjustment method to the noise power
adjustment method. Valid range is from 10 through 100 percent.