|
|
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.
Table 1 lists the IOS cable router features released in the IOS 12.0 timeframe.
| Available With: | Category | Feature |
|---|---|---|
11.3(5)NA & 12.0(3)T | Cable Features | Feature Enhancements |
11.3(6)NA |
| MC16 Modem Card |
11.3(8)NA |
| Access List Support Enhancements |
12.0(4)T |
| Downstream Channel ID Configuration |
12.0(4)T |
| Multiple Service ID Support |
12.0(4)T |
| Cable Modem and Host Subnet Addressing |
12.0(5)T |
| Telephone Return |
12.0(5)T |
| Time Server Functionality |
12.0(7)T |
| Amplitude Averaging Compensation |
12.0(7)XR |
| Cable Interface Bundling |
12.0(7)XR |
| Enhanced Modem Status Display |
12.0(7)XR |
| Show Interface Cable Command Verbose Enhancements |
12.0(7)XR |
| IP Address Verification |
12.0(7)XR |
| Registration Timeout Configuration |
12.0(7)XR |
| Show Cable Modem Command Enhancements |
12.0(7)XR |
| Modem Status Summary Enhancements |
12.0(7)XR |
| Show Controller Command Enhancements |
12.0(7)XR |
| Configuring Concatenation |
12.0(7)XR |
| Virtual Private Network Support |
12.0(7)XR |
| Blind Hopping Support on the MC16S Modem Card |
12.0(7)XR |
| Signal-to-Noise Ratio Data Support |
11.3(9)NA and 12.0(4)T | Cable QoS | QoS Profile Enforcement |
12.0(4)T |
| Quality of Service for Voice |
11.3(9)NA | Network Management | Upstream Traffic Shaping Feature |
12.0(5)T |
| Enhanced-Spectrum Management |
12.0(5)T |
| Downstream Rate Shaping with TOS bits |
12.0(7)XR |
| Spectrum Management Using the MC16S Modem Card |
12.0(7)XR |
| Downstream Test Signals Configuration |
12.0(7)XR | Wireless Features | Point-to-Point Wireless Support |
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:
uBR7200 series cable router
No new or modified MIBs are supported by this feature.
No new or modified MIBs are supported by this feature.
No new or modified RFCs are supported by this feature.
None
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-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 * 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 modem
Interface Prim Online Timing Rec QoS CPE IP address MAC address
Sid State Offset Power
Cable3/0/U0 1 online 2257 0.00 3 0 10.30.128.142 0090.8330.0217
Cable3/0/U0 2 online 2262 *-0.50 3 0 10.30.128.145 0090.8330.020f
Cable3/0/U0 3 online 2260 0.25 3 0 10.30.128.146 0090.8330.0211
Cable3/0/U0 4 online 2256 *0.75 3 0 10.30.128.143 0090.8330.0216
Cable3/0/U0 5 online 2265 *0.50 3 0 10.30.128.140 0090.8330.0214
Cable3/0/U0 6 online 2256 0.00 3 0 10.30.128.141 0090.8330.0215
Cable3/0/U0 7 online 4138 !-1.00 3 1 10.30.128.182 0050.7366.124d
Cable3/0/U0 8 online 4142 !-3.25 3 1 10.30.128.164 0050.7366.1245
Cable3/0/U0 9 online 4141 !-3.00 3 1 10.30.128.185 0050.7366.17e3
Cable3/0/U0 10 online 4142 !-2.75 3 0 10.30.128.181 0050.7366.17ab
Cable3/0/U0 11 online 4142 !-3.25 3 1 10.30.128.169 0050.7366.17ef
As 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.
None
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.
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]}
n | Specifies the upstream port number. |
threshold # | Specifies the power adjustment threshold. The threshold range is from 0 to 10dB. 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%. The default is 30%. |
Threshold default is 1 dB, the tolerable value default is 2 dB, and the power adjustment is 30%.
Interface configuration
| Release | Modification |
|---|---|
12.0(7)T | This command was introduced. |
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 50
| Command | Description |
|---|---|
cable upstream freq-adj | Control power adjustment methods by setting the frequency threshold. |
show cable flap | Displays the quality of the connection for downstream modems. Information includes power adjustment flags showing where noise power adjustments are used. |
show cable modem | Displays the status of connected modems, including receive power conditions that are having problems. |
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
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 to 100%. |
No default behavior or values.
Interface configuration
| Release | Modification |
|---|---|
12.0(7)T | This command was introduced. |
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 50
| Command | Description |
|---|---|
cable upstream power adjust | Controls power adjustment methods by setting the noise threshold. |
show cable flap | Displays the quality of the connection for downstream modems. Information includes power adjustment flags showing where noise power adjustments are used. |
show cable modem | Displays the status of connected modems, including receive power conditions that are having problems. |
Posted: Fri Jan 21 18:17:38 PST 2000
Copyright 1989 - 2000©Cisco Systems Inc.