Performing Amplitude Averaging; Enabling Or Disabling Power Adjustment - Cisco 7246VXR - uBR Router Software Configuration Manual

Chapter 8 Troubleshooting the System

Performing Amplitude Averaging

The Cisco uBR7200 series 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 Cisco uBR7200 series CMTS averages a configurable
number of RNG-REQ messages before it makes power adjustments. By compensating for a potentially
unstable return path, the Cisco uBR7200 series 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 Cisco uBR7200 series 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
0010.7bb3.fd19
0010.7bb3.fcfc
0010.7bb3.fcdd
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
0050.04f9.edf6 10.44.51.49
0050.04f9.efa0 10.44.51.48
0030.d002.41f5 10.44.51.147
0030.d002.4177 10.44.51.106
0030.d002.3f03 10.44.51.145
0050.04f9.ee24 10.44.51.45
0030.d002.3efd 10.44.51.143
0030.d002.41f7 10.44.51.140
0050.04f9.eb82 10.44.51.53
0050.f112.3327 10.44.51.154
0030.d002.3f8f 10.44.51.141
0001.64f9.1fb9 10.44.51.55
0030.d002.417b 10.44.51.146
0090.9600.6f7d 10.44.51.73
0010.9501.ccbb 10.44.51.123
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:
•
•

Enabling or Disabling Power Adjustment

To enable the power-adjustment capability, use the cable upstream power-adjust command in interface
configuration mode:
OL-2239-03
Upstream
Cable5/0/U1
Cable5/0/U1
Cable5/0/U1
IP Address
cable upstream power-adjust noise
cable upstream frequency-adjust averaging
Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
Ins Hit Miss CRC
0 2792 281 0
0 19 4 0
0 19 4 0
I/F MAC
State
C7/1/U0 online 1
C7/1/U0 online 2
C7/1/U0 online 3
C7/1/U0 online 4
C7/1/U0 online 5
C7/1/U0 online 6
C7/1/U0 online 7
C7/1/U0 online 8
C7/1/U0 online 9
C7/1/U0 online 10
C7/1/U0 online 11
C7/1/U0 online 12
C7/1/U0 online 13
C7/1/U0 online 14
C7/1/U0 online 15
Performing Amplitude Averaging
P-Adj Flap Time
*45 58 Jul 27 16:54:50
!43 43 Jul 27 16:55:01
*3 3 Jul 27 16:55:01
Prim RxPwr Timing Num
Sid (db) Offset CPEs Enbld
-0.50 3757 0 no
-0.50 3757 0 no
-0.25 3829 0 no
-0.50 3798 0 no
0.25 3827 0 no
-1.00 3757 0 no
-0.25 3827 0 no
0.00 3814 0 no
-0.50 3756 0 no
0.25 3792 0 no
0.00 3806 0 no
0.00 4483 0 no
0.50 3812 0 no
0.00 4071 0 no
0.25 3691 0 no
BPI
8-7