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Chapter 8
Troubleshooting ISDN
The debug command is assigned a high CPU priority and can generate a
high processor load. Always use caution when using a debug command.
The resulting processor load and output can degrade router performance
or render the system unusable.
It is recommended that routers be configured with timestamps for debug and
log output. Use the service timestamps debug datetime msec show-timezone
localtime
command to provide debug time information.
debug bri
The debug bri command provides information regarding the B channels of
the BRI. An example of the command's output is provided below. Note that
bandwidth information is also provided.
The B channels of the BRI are the data-carrying channels; therefore, an
error in the activation of a B channel prevents data flow. It is also possible for
the router to command one B channel to connect while the other B channel
fails, which may be due to a misconfigured SPID or configuration problem.
This command provides some insight into this potential problem.
Bottom#debug bri
Basic Rate network interface debugging is on
Bottom#ping 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2
seconds:
00:29:48: BRI: enable channel B1
00:29:48: BRI0:MC145572 state handler current state 3
actions 1 next state 3
00:29:48: BRI0:Starting activation
00:29:48: %LINK-3-UPDOWN: Interface BRI0:1, changed state
to up.
00:29:49: BRI 0 B1: Set bandwidth to 64Kb
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