Installation guide

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Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 5 Troubleshooting the System
Performing Amplitude Averaging
Similar to the show cable flap-list display, the * symbol in the show cable modem output indicates that
the CMTS is using the power adjustment method on this CM. The ! symbol indicates that the CM has
reached maximum transmit power.
This section documents the commands pertaining to amplitude averaging:
• cable upstream power-adjust noise
• cable upstream frequency-adjust averaging
Enabling or Disabling Power Adjustment
To enable or disable the power adjustment capability, use the following commands:
cable upstream n power-adjust {threshold [threshold #] | continue [tolerable value] | noise [% of
power adjustment]}
no cable upstream power-adjust
Note The threshold default is 1 dB. The tolerable value default is 2 dB. The power adjustment is 30 percent.
Caution Default settings are adequate for system operation. Amplitude averaging is an automatic procedure. In
general, Cisco does not recommend you adjust values. Cisco does recommend, however, that you clean
up your cable plant should you encounter flapping cable modems.
Note In some instances, you might adjust certain values:
If CMs cannot complete ranging because they have reached maximum power levels, you might try to set
the tolerable value CONTINUE field to a larger value than the default of 2 dB. Values larger than 10 dB
on “C” versions of cable modem cards, or 5 dB on FPGA versions, are not recommended.
If the flap list shows CMs with a large number of power adjustments, but the CMs are not detected as
“noisy,” you might try to decrease the percentage for “noisy.” If you think too many CMs are
unnecessarily detected as “noisy,” you might try to increase it.
Table 5-9 Cable Upstream Power Adjust Syntax Descriptions
Syntax Description
n
Specifies the upstream port number.
threshold #
Specifies the power adjustment threshold. The threshold range is from 0
to 10 dB. The default is 1 dB.
tolerable value
Determines if the status of the RNG-RSP should be set to CONTINUE or
SUCCESS. The range is from 2 to 15 dB. The default is 2 dB.
% of power adjustment
Specifies the percentage of power adjustment packets required to switch
from the regular power adjustment method to the noise power adjustment
method. Range is from 10 to 100 percent. The default is 30 percent.