Installation guide

5-33
Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 5 Troubleshooting the System
Troubleshooting Cable Flap Lists
The following tips and scenarios allow you to use the flap list in the most effective way:
• If a subscriber's cable interface shows a lot of flap list activity, it is having communication problems.
• If a subscriber's cable interface shows little or no flap list activity, it is communicating reliably; the
problem is probably in the subscriber's computer equipment or in the connection to the
cable interface.
• The top 10% most active cable interfaces in the flap list are most likely to have difficulties
communicating with the headend.
• Cable modems with more than 50 power adjustments per day have a suspect upstream path.
• Cable modems with approximately the same number of hits and misses and with a lot of insertions
have a suspect downstream path (for example, low level into the cable interface).
• All cable interfaces incrementing the insertion at the same time indicates a provisioning server
failure.
• Cable modems with high CRC errors have bad upstream paths or in-home wiring problems.
• Correlating cable interfaces on the same physical upstream port with similar flap list statistics can
quickly resolve outside plant problems to a particular node or geography.
• Monitoring the flap list cannot affect cable interface communications.
• The flap list should be saved to a database computer and cleared at least once each day.
• Important upstream performance data can be obtained by tracking flap list trend data.
• Important installation quality control and performance data is directly available from the flap list.
Following is a sample response to the show cable flap command:
uBR7100# show cable flap
Mac Addr CableIF Ins Hit Miss CRC P-Adj Flap Time
0010.9500.461f C1/0 U1 56 18857 887 0 1 116 Jun 1 14:09:12
0010.9500.446e C1/0 U1 38 18686 2935 0 1 80 Jun 2 19:03:57
0010.9500.38ec C1/0 U2 63 18932 1040 0 8 138 Jun 2 23:50:53
0010.9500.4474 C1/0 U2 65 18913 1053 0 3 137 Jun 2 09:30:09
0010.9500.4672 C1/0 U2 56 18990 2327 0 6 124 Jun 2 10:44:14
0010.9500.38f0 C1/0 U2 50 18964 2083 0 5 111 Jun 2 20:46:56
0010.9500.e8cb C1/0 U2 0 6537 183 0 1 5 Jun 2 22:35:48
0010.9500.38f6 C1/0 U3 50 19016 2511 0 2 104 Jun 2 07:46:31
0010.9500.4671 C1/0 U3 43 18755 3212 1 1 89 Jun 1 19:36:20
0010.9500.38eb C1/0 U0 57 36133 1608 0 6 126 Jun 2 20:04:58
0010.9500.3ce2 C1/0 U0 44 35315 1907 0 4 99 Jun 2 16:42:47
0010.9500.e8d0 C1/0 U2 0 13213 246 0 1 5 Jun 3 04:15:30
0010.9500.4674 C1/0 U2 56 36037 2379 0 4 121 Jun 3 00:34:12
0010.9500.4677 C1/0 U2 40 35781 2381 0 4 91 Jun 2 12:14:38
0010.9500.4614 C1/0 U2 40 21810 2362 0 502 586 Jun 2 21:43:02
0010.9500.3be9 C1/0 U2 63 22862 969 0 0 128 Jun 1 14:09:03
0010.9500.4609 C1/0 U2 55 22723 2127 0 0 112 Jun 1 14:08:02
0010.9500.3cb8 C1/0 U2 49 22607 1378 0 0 102 Jun 1 14:08:58
0010.9500.460d C1/0 U3 46 22477 2967 0 2 96 Jun 2 17:03:48
0010.9500.3cba C1/0 U3 39 22343 3058 0 0 81 Jun 1 14:13:16
0010.9500.3cb4 C1/0 U3 38 22238 2936 0 0 79 Jun 1 14:09:26
0010.9500.4612 C1/0 U3 38 22306 2928 0 0 79 Jun 1 14:09:29
The command line with an arrow next to it reveals a cable interface that is continuously flapping. A high
flap rate indicates that the cable interface is power adjusting frequently. This can indicate a problem with
an amplifier. The number reveals the number of times the CMTS instructed the cable interface to adjust
the transmit power more than 3 dB.
Cable modems are automatically added to the flap list when any of the following conditions are detected: