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debug command

Level 1
Level 1

I would like to know how to display the debug output!

my IOS is 12.4

for example, i am trying:

3845# debug vpdn event

and all i get is:

VPDN events debugging is on

that's it! how can i see the debug output?

7 Replies 7

Level 9
Level 9

Debug output is only sent to the console by default. If you are executing the command from a telnet session you need to redirect/copy the output to your session.

The command for that is: term mon




yes i am in telnet.

I did #term monitor

then #debug vpdn event

i got the same message :

VPDN events debugging is on

is the debug output is being copied somewhere?


Where and how the debug output is copied depends on how the router is configured. Debug creates log records with severity level 7. As the previous post says by default debug output (severity level 7) is sent to the console. It can be suppressed from the console by changing the severity level of logging to the console. The debug output is also normally available to the terminal monnitor, though the severity level of terminal monitor can also be adjusted. If you have configured logging buffer the syslog messages will be copied to the log buffer (where you can see them using the show log command). You can also configure logging to a syslog server to send debug messages to the syslog server (though most places that I work with do not do this since they do not want the load of the debug output on the syslog server).

If you do the command show log the first group of messages in the output will show the various logging destinations and the severity level of messages being sent to each one. Do the show log and check for which destinations are enabled and are receiving debug (severity level 7) messages.





To get any output from the debugger, it is vital that there is something to debug. Eventually you may use another debug command to verify that you are getting results.

The debugger is a real-time tool, it does not show any history. However, when you are using the command "logging buffered" the last few kb of data are preserved. use the command "sh logg" to display the buffer contents.




Do you mean after i debug an interface, if there is no immediate output, it will always show later on when i apply #sh logging ?

what i did:


#loggin on

#logging monitor 7

then i debugged my dsl connection (vpdn event & dialer)

after i #sh logging

i havent got any output in regard of these 2 elemts, all the events that were there is an async interface changed status to either up or down.

my DSL is not working, and i would like to debug to see what's the issue, i have waited for several hours, and nothing in regards of vpdn nor dialer has shown in #sh logging so far.

any clue?

If you are telneted in, enabled 'term mon', turned on the debug and still don't see any output then it sounds like the 'debug vpdn events' has no events to display. Can you try enabling 'debug vpdn packet' and see if that helps you with your troubleshooting.



When your interface is not working you will get little output from the vpdn events debug.

You should rather concentrate on the status of your ATM interface and the status of the ppp dialer (if applicable).

Verify the configuration and make sure that you have used the correct VP/VC for your ATM connection. Personally, I find the use of "deb ppp neg" quite useful for the following stage where you verfiy the connection to the provider. Usually there are no problems once that is OK.

Please post the config if you need assistance on how to do this.