Table Of Contents
Amplitude Averaging Compensation on the Cisco uBR7200 Series Cable Router
Related Features and Technologies
Supported Standards, MIBs, and RFCs
cable upstream freq-adj averaging
Amplitude Averaging Compensation on the Cisco uBR7200 Series Cable Router
Feature Overview
Occasionally, the headend cable router drops modems with low Carrier-to-Noise ratios when making excessive power adjustments in response to ring-request (RNG-REQ) messages from affected modems. A solution to this problem of dropping modems is to have the cable router average a configurable number of RNG-REQ messages before making power adjustments. By compensating for a potentially unstable return path, the uBR router can maintain connectivity. However, you can interpret these power adjustments as indicating an unstable return path connection.
The show cable flap-list and show cable modem commands have been expanded to indicate which paths the cable router is making power adjustments and which modems have already reached maximum transmit power settings. Treat the marked paths as those that need service.
Benefits
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You can now configure cable router power adjustments to optimize cable operations under less than ideal conditions.
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Related Features and Technologies
lists the IOS cable router features released in the IOS 12.0 timeframe.
Table 1 uBR7200 Series Cable Router Features Available Since 12.0 T
Related Documents
The uBR7200 series cable router is described in Voice, Video, and Home Applications Configuration Guide for Cisco IOS Release 12.0 and in the following online feature modules:
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Supported Platforms
uBR7200 series cable router
Supported Standards, MIBs, and RFCs
Standards
No new or modified MIBs are supported by this feature.
MIBs
No new or modified MIBs are supported by this feature.
RFCs
No new or modified RFCs are supported by this feature.
Configuration Tasks
None
Monitoring Power Adjustments
Enter the show cable flap or the show cable modem commands to see where the cable modem termination system (CMTS) is making power adjustments and track which modems have reached maximum transmit power. Both these conditions indicate possible unstable paths that should be serviced.
The following example shows the output of the show cable flap-list command:
router# show cable flap-listMAC Address Upstream Ins Hit Miss CRC P-Adj Flap Time0010.7bb3.fd19 Cable5/0/U1 0 2792 281 0 *45 58 Jul 27 16:54:500010.7bb3.fcfc Cable5/0/U1 0 19 4 0 !43 43 Jul 27 16:55:010010.7bb3.fcdd Cable5/0/U1 0 19 4 0 *3 3 Jul 27 16:55:01The * symbol indicates the CMTS is using the power adjustment method on this modem. The ! symbol indicates the modem has reached maximum transmit power.
The following example shows the output of the show cable modem command:
router# show cable modemInterface Prim Online Timing Rec QoS CPE IP address MAC addressSid State Offset PowerCable3/0/U0 1 online 2257 0.00 3 0 10.30.128.142 0090.8330.0217Cable3/0/U0 2 online 2262 *-0.50 3 0 10.30.128.145 0090.8330.020fCable3/0/U0 3 online 2260 0.25 3 0 10.30.128.146 0090.8330.0211Cable3/0/U0 4 online 2256 *0.75 3 0 10.30.128.143 0090.8330.0216Cable3/0/U0 5 online 2265 *0.50 3 0 10.30.128.140 0090.8330.0214Cable3/0/U0 6 online 2256 0.00 3 0 10.30.128.141 0090.8330.0215Cable3/0/U0 7 online 4138 !-1.00 3 1 10.30.128.182 0050.7366.124dCable3/0/U0 8 online 4142 !-3.25 3 1 10.30.128.164 0050.7366.1245Cable3/0/U0 9 online 4141 !-3.00 3 1 10.30.128.185 0050.7366.17e3Cable3/0/U0 10 online 4142 !-2.75 3 0 10.30.128.181 0050.7366.17abCable3/0/U0 11 online 4142 !-3.25 3 1 10.30.128.169 0050.7366.17efAs above, the * symbol indicates the CMTS is using the power adjustment method on this modem. The ! symbol indicates the modem has reached maximum transmit power.
Configuration Examples
None
Command Reference
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command reference publications.
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cable upstream power-adjust
To control power adjustment methods by setting the noise threshold, use the cable upstream power-adjust noise interface configuration command. To disable power adjustments, use the no form of this command.
cable upstream n power-adjust {threshold [threshold #] | continue [tolerable value] | noise [% of power adjustment]}
no cable upstream power-adjust
Syntax Description
Defaults
Threshold default is 1 dB, the tolerable value default is 2 dB, and the power adjustment is 30%.
Command Modes
Interface configuration
Command History
Examples
The following example show how to change the power adjustment method when the percentage of power adjustment packets reaches 50%:
router(config-if)# cable upstream 0 power-adjust noise 50Related Commands
cable upstream freq-adj averaging
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
Syntax Description
Defaults
No default behavior or values.
Command Modes
Interface configuration
Command History
Examples
The following example shows how to change the power adjustment method when the frequency adjustment packet count reaches 50%:
router(config-if)# cable upstream 0 freq-adj averaging 50Related Commands