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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-03
Chapter8 Troubleshooting the System
Performing Amplitude Averaging
Performing Amplitude Averaging
The CiscouBR7200series CMTS uses an averaging algorithm to determine the optimum power level
for a CM with low carrier-to-noise ratio that is making excessive power adjustments—known as
flapping. To avoid dropping flapping CMs, the CiscouBR7200series CMTS averages a configurable
number of RNG-REQ messages before it makes power adjustments. By compensating for a potentially
unstable return path, the CiscouBR7200series CMTS maintains connectivity with affected CMs. You
can interpret these power adjustments, however, as indicating unstable return path connections.
The show cable flap-list and show cable modem commands are expanded to indicate the paths on which
the CiscouBR7200series CMTS is making power adjustments and the modems that have reached
maximum transmit power settings. These conditions indicate unstable paths that should be serviced.
The following example shows the output of the show cable flap-list command:
Router# show cable flap-list
MAC Address Upstream Ins Hit Miss CRC P-Adj Flap Time
0010.7bb3.fd19 Cable5/0/U1 0 2792 281 0 *45 58 Jul 27 16:54:50
0010.7bb3.fcfc Cable5/0/U1 0 19 4 0 !43 43 Jul 27 16:55:01
0010.7bb3.fcdd Cable5/0/U1 0 19 4 0 *3 3 Jul 27 16:55:01
The asterisk (*) indicates that the CMTS is using the power-adjustment method on this modem. An
exclamation point (!) indicates that the modem has reached maximum transmit power.
Output of the show cable modem command appears below:
Router# show cable modem
MAC Address IP Address I/F MAC Prim RxPwr Timing Num BPI
State Sid (db) Offset CPEs Enbld
0050.04f9.edf6 10.44.51.49 C7/1/U0 online 1 -0.50 3757 0 no
0050.04f9.efa0 10.44.51.48 C7/1/U0 online 2 -0.50 3757 0 no
0030.d002.41f5 10.44.51.147 C7/1/U0 online 3 -0.25 3829 0 no
0030.d002.4177 10.44.51.106 C7/1/U0 online 4 -0.50 3798 0 no
0030.d002.3f03 10.44.51.145 C7/1/U0 online 5 0.25 3827 0 no
0050.04f9.ee24 10.44.51.45 C7/1/U0 online 6 -1.00 3757 0 no
0030.d002.3efd 10.44.51.143 C7/1/U0 online 7 -0.25 3827 0 no
0030.d002.41f7 10.44.51.140 C7/1/U0 online 8 0.00 3814 0 no
0050.04f9.eb82 10.44.51.53 C7/1/U0 online 9 -0.50 3756 0 no
0050.f112.3327 10.44.51.154 C7/1/U0 online 10 0.25 3792 0 no
0030.d002.3f8f 10.44.51.141 C7/1/U0 online 11 0.00 3806 0 no
0001.64f9.1fb9 10.44.51.55 C7/1/U0 online 12 0.00 4483 0 no
0030.d002.417b 10.44.51.146 C7/1/U0 online 13 0.50 3812 0 no
0090.9600.6f7d 10.44.51.73 C7/1/U0 online 14 0.00 4071 0 no
0010.9501.ccbb 10.44.51.123 C7/1/U0 online 15 0.25 3691 0 no
The asterisk (*) in the show cable modem command 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 the power-adjustment capability, use the cable upstream power-adjust command in interface
configuration mode: