Troubleshooting Tips for the Cisco uBR924 Cable Access Router 1
Troubleshooting Tips for the Cisco uBR924 Cable Access Router

Feature Summary

This document describes the Cisco IOS troubleshooting commands that may be used by cable
service providers to verify communication between a Cisco uBR924 cable access router and other
peripheral devices installed in the HFC headend such as a CiscouBR7200 series universal
broadband router, a DHCP server, and a TFTP server.
Benefits The Cisco uBR924 cable access router troubleshooting system provides the following benefits:
•A MAC-layer system log file that provides a snapshot of detailed reasons why an interface might
reset, along with all the negotiations that occurred between the Cisco uBR924 cable access router
and the CMTS. Over 220 possible description fields exist in this log, which is displayed using the
show controllers cable-modem 0 mac log command from privileged EXEC mode.
•Debug does not need to be turned on in order to troubleshoot a Cisco uBR924 cable access router.
•The progression of normal data-over-cable communication events is clearly explained,
simplifying the resolution of faulty system connections.
•Troubleshooting and diagnostic tasks can be performed on the Cisco uBR924 from a remote
location using TELNET.
RestrictionsWhen using the Cisco uBR924 cable ac cess router, k eep the following restrictions and limitations in
mind:
•The Cisco uBR924 is able to implement multiple classes of service (CoS) on the cable interface;
however, separate CoS streams are only available when the cable access router is connected to a
headend that supports multiple CoS per cable access router. In addition, the configuration file
downloaded to the cable access router must specify the use of multiple classes of service.
•If the Cisco uBR924 cable access router is connected to a DOCSIS 1.0 headend that does not
support multiple CoS per cable access router, voice and data will be mixed, and voice traffic will
be transmitted on a best effort basis. This may cause poorer voice quality and lower data
throughput when calls are being made from the cable access router’s telephone ports. Voice
quality may also be affected when transmitting or downloading large files, or at other times when
network traffic is heavy.