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Troubleshooting Tips for the Cisco uBR904 Cable Modem 1
Troubleshooting Tips for the
Cisco uBR904 Cable Modem
The following sections are provided:
• Feature Summary on page 1
• Prerequisites on page 3
• Supported MIBs and RFCs on page 3
• CMTS to Cable Modem Network Topology on page 4
• Troubleshooting Tips on page 5
• Command Reference on page 16
• Debug Commands on page 42
• What to do Next on page 54
Feature Summary
This document provides MSOs (multiple service operators) with a set of software tools for
troubleshooting a cable modem for data-over-cable connections. These tools are Cisco IOS
troubleshooting commands used for verifying communication between the cable modem and other
peripheral devices installed in the HFC network, such as the headend Cisco uBR7246, a DHCP
server, and TFTP server.
Benefits
• A MAC layer system log file exists inside the cable modem, which provides you with a snapshot
of detailed reasons why an interface might reset and all the negotiations that occurred between
the cable modem and the CMTS (a Cisco uBR7246 positioned at the headend). Over 220 possible
description fields exist in this log. The log is displayed using the show controller cable-modem
0 mac log EXEC command.
• Debug does not need to be turned on to troubleshoot a cable modem.
• Cable technicians can understand the progression of normal data-over-cable communication
events, from which they can resolve faulty system connections.
• A cable technician can remotely telnet into a Cisco uBR904 cable modem, which could be
installed in a customer’s home, and perform simple diagnostic tasks.