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Debug Commands
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Release 11.3(4)NA
debug cable-modem mac
Use the debug cable-modem mac Privileged EXEC command to troubleshoot the cable modem
MAC layer. The no form of this command turns debugging messages off.
[no] debug cable-modem mac {log [verbose] | messages}
Syntax Description
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3 NA.
Of all the available debug cable modem commands, the most useful is debug cable-modem mac
log.
Mac log messages are written to a circular log file even when debugging is not turned on. These
messages include timestamps, events, and information pertinent to these events. Enter the debug
cable-modem mac log command to view Mac log messages. If you want to view this information
without entering debug mode, enter the show controller cable-modem number mac log command.
The same information is displayed by both commands.
If the cable modem interface fails to come up or resets periodically, the Mac log will show what
happened. For example, if an address is not obtained from the DHCP server, an error is logged,
initialization starts over, and the cable modem scans for a downstream frequency. The debug
cable-modem mac log command displays the log from oldest entry to newest entry.
After initial ranging is successful (dhcp_state has been reached), further
RNG-REQ/RNG-RSP
messages and watchdog timer entries are suppressed from output, unless the verbose keyword suffix
is used. For example, the debug cable-modem mac log verbose command is entered. Note that
CMAC_LOG_WATCHDOG_TIMER entries while in the maintenance_state are normal when using the
verbose keyword.
Sample Displays
Figure 8 shows sample display output from the debug cable-modem mac log Privileged EXEC
command. After the debug command is entered, the fields of the output are: the date, local time,
seconds since bootup, the log message, and in some cases a parameter that gives more detail about
the log entry.
The line “
0 events dropped due to lack of a chunk” at the end of a display indicates that no
log entries were discarded due to a temporary lack of memory. This means the log is accurate and
reliable.
log Realtime MAC log display.
verbose (Optional) Displays periodic MAC layer events, such as ranging.
messages MAC layer management messages.