Chapter 4 Troubleshooting the System

Troubleshooting Using Cable Flap Lists

Set Cable Flap List Power Adjustment Threshold

You can specify the power adjustment threshold that will cause a flap-list event to be recorded. When the power adjustment of a cable modem meets or exceeds the threshold, the cable modem is placed in the flap list. The valid range is from 1 to 10 dBmV.

Note A power adjustment threshold of less than 2 dBmV might cause excessive flap list event recording. Cisco recommends setting this threshold value to 3 dBmV or higher.

To set the power adjustment threshold for flap-list events, use the following command in global configuration mode.

Table 4-23 Instruction to Set Cable Flap List Power Adjustment Threshold

Command

Purpose

 

 

CMTS01(config)# cable flap-list power-adjust threshold dbmv

Specify the minimum power adjustment that will

 

constitute a flap-list event.

 

 

Verify Cable Flap List Power Adjustment Threshold

To verify the cable flap list power adjustment threshold, enter the show cable flap list command:

CMTS01# show cable flap list

 

 

 

 

 

 

 

Mac Addr

CableIF

Ins

Hit

Miss

CRC

P-Adj

Flap

Time

 

0010.7b6b.5d1d

C3/0 U0

0

688

169

0

0

3

Nov 5

12:28:50

0010.7b6b.5e15

C3/0 U0

1

707

185

0

0

5

Nov 5

12:29:52

0010.7b6b.5e27

C3/0 U0

1

707

198

0

0

5

Nov 5

12:29:55

0010.7b6b.5d29

C3/0 U0

1

709

205

0

0

5

Nov 5

12:29:52

0010.7b6b.5e2b

C3/0 U0

1

710

204

0

0

7

Nov 5

12:30:16

Set Cable Flap List Miss Threshold

You can specify the miss threshold for recording a flap-list event. A miss is the number of times a cable modem does not acknowledge a MAC layer keepalive message from a cable modem card. An 8% miss rate is normal for the Cisco cable modem cards. When the number of misses exceeds the threshold, the cable modem is placed in the flap list.

Note A high miss rate can indicate intermittent upstream problems, fiber laser clipping, or common-path distortion.

To set the miss threshold for recording a flap-list event, use the following command in global configuration mode.

Table 4-24 Instructions to Set Cable Flap List Miss Threshold

 

Command

Purpose

 

 

 

 

CMTS01(config)# cable flap-list miss-threshold misses

Specify the number of MAC-layer keepalive misses

 

 

 

 

that will result in the cable modems being place in

 

 

 

 

the flap list.

 

 

 

 

 

 

 

 

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

 

 

 

 

 

 

 

 

 

 

4-42

 

 

78-5897-01

 

 

 

 

 

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Cisco Systems uBR7200 Series manual Set Cable Flap List Power Adjustment Threshold, Set Cable Flap List Miss Threshold