Installation guide
5-40
Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 5 Troubleshooting the System
Troubleshooting Cable Flap Lists
Setting 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 interface card. An 8%
miss rate is normal for the Cisco cable interface cards. When the number of misses exceeds the
threshold, the cable interface 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.
Verifying Cable Flap List Miss Threshold
To verify the cable flap list miss 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 C1/0 U0 0 688 169 0 0 3 Nov 5 12:28:50
0010.7b6b.5e15 C1/0 U0 1 707 185 0 0 5 Nov 5 12:29:52
0010.7b6b.5e27 C1/0 U0 1 707 198 0 0 5 Nov 5 12:29:55
0010.7b6b.5d29 C1/0 U0 1 709 205 0 0 5 Nov 5 12:29:52
0010.7b6b.5e2b C1/0 U0 1 710 204 0 0 7 Nov 5 12:30:16
Setting Cable Flap List Size
You can specify the maximum number of cable interfaces that can be listed in the cable flap list tables.
The valid range is from 1 to 8192 cable interfaces. The default is 8192 cable interfaces.
To specify the maximum number of cable modems that can be recorded in the flap list, use the following
command in global configuration mode.
Verifying Cable Flap List Size
To verify the cable flap list size, 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 C1/0 U0 0 688 169 0 0 3 Nov 5 12:28:50
0010.7b6b.5e15 C1/0 U0 1 707 185 0 0 5 Nov 5 12:29:52
0010.7b6b.5e27 C1/0 U0 1 707 198 0 0 5 Nov 5 12:29:55
0010.7b6b.5d29 C1/0 U0 1 709 205 0 0 5 Nov 5 12:29:52
0010.7b6b.5e2b C1/0 U0 1 710 204 0 0 7 Nov 5 12:30:16
Command Purpose
CMTS01(config)# cable flap-list
miss-threshold
misses
Specifies the number of MAC layer keepalive misses that
will result in the cable modems being place in the flap list.
Command Purpose
CMTS01(config)# cable flap-list size number
Specifies the maximum size of the flap list.