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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
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Chapter4 Troubleshooting the System
Troubleshooting Using Cable Flap Lists
Table4-20 Flap List Statistics Description
Statistic Description
MAC ID This is the MAC-layer address of a cable modem. The first six digits indicate the vendor ID of
the cable modem manufacturer, followed by six digits indicating a unique host address. Each
cable modem's MAC address is unique.
Cable IF This is the physical upstream interface on the Cisco uBR7200. Itdenotes the cable modemcard
slot number,the downstream port number on the RF line card and the upstream port number on
thesame cable modem card. The flap list data can be sorted based on the upstream port number
which is useful when isolating reverse path problems unique to certain combining groups.
Insertions Link insertion is the process whereby a modem performs an initial maintenance procedure to
establish link with the CMTS. The Ins column is the flapping modem’s insertion count and
indicates the number of times the RF link was abnormally re-established. An abnormality is
detectedwhen the time between link re-establishment attempts is less than the user-configurable
parameter.
Normal modem activity follows the sequence below.
•The initial link insertion is followed by a keepalive loop between the CMTS and cable
modem and is called station maintenance.
•Power-on
•Initial maintenance
•Station maintenance
•Power-off
When the link is broken, initial maintenance is repeated to re-establish the link.
Initial maintenance @ Time T1
Station maintenance
Init maintenance @ Time T2
TheIns and Flap counters in the flap list are incremented whenever T2 – T1 < N where N is the
insertion-time parameter configured in<cable flap-list insertion-time>. Default value for this
parameter is TBD seconds.
A high Ins number indicates:
•Intermittent downstream sync loss
•DHCP or modem registration problems