Installation guide

5-35
Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 5 Troubleshooting the System
Troubleshooting Cable Flap Lists
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 detected when
the time between link re-establishment attempts is less than the
user-configurable parameter.
Normal modem activity uses the following sequence below.
• 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
The Ins 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>.
A high Ins number indicates:
• Intermittent downstream sync loss
• DHCP or modem registration problems
Table 5-8 Flap List Statistics Description (continued)
Statistic Description