Troubleshooting guide

Troubleshooting the CMTS
4-41
Introduction
This chapter provides troubleshooting solutions to some common Data Over Cable
Service Interface Specifications (DOCSIS) network problems with the following:
• Using Flap Lists to Troubleshoot CM Problems
• Resolving HFC Network Performance Problems
• Resolving Problems on the Upstream Path
• Resolving Problems on the Downstream Path
• Resolving Cable Modem Problems
Using Flap Lists to Troubleshoot CM Problems
The BSR maintains a database of flapping CMs to assist in locating cable plant
problems. The flap list feature tracks the upstream and downstream performance
of all CMs on the network, without impacting throughput and performance
between the CM and BSR, or creating additional packet overhead on the HFC
network.
Refer to the BSR 64000 Configuration and Management Guide for more
information on configuring flap-list settings.
Viewing Flap List Statistics to Identify Network Health
Flap lists are used to collect statistics for determining CM problems on the
network. There are several different options for sorting flap list statistics. The CM
flap list keeps track of the CM MAC address, up and down transitions, registration
events, missed periodic ranging packets, upstream power adjustments on the BSR.
This section describes the different sorting options and describes the command
output fields.
CMs appear in the flap list when any of the following conditions are detected:
• The CM re-registers more frequently than the configured insertion time.
• Intermittent keepalive messages are detected between the BSR and the CM.