ISDN router dialing out needlessly

Unanswered Question
Jul 6th, 2009
User Badges:

I have a 3640 router that is effectively configured on our network as ISDN dial up for backup in case our Frame Relay network fails.

My manager brought me a phone bill from our provider earlier. Last month we found that on some days, this router is dialing out some of the ISDN connections

over and over again, many times within the same minute. This is causing issues as the phone company is billing us for each call

I need some help in understanding why this router is behaving in this unorthodox capacity. I have been running "debug isdn events" this afternoon, but this afternoon, the router has not been dialing out any..

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
shillyar Mon, 07/06/2009 - 11:27
User Badges:
  • Cisco Employee,


please add access-list xxx deny ip any host to your dialer list and then run debug dialer and see what triggering the dial.

send in your dialer debugs when it dials and your confs as this should be a straight forward fix once we know whats trigger the isdn line.

Thx Steve

Kevin Melton Mon, 07/06/2009 - 12:45
User Badges:

When you say "please add access-list xxx deny ip any host to your dialer list".. what host do I put after host?...

I have the following debug's running:

Dial on demand:

Dial on demand events debugging is on


ISDN events debugging is on

ISDN events debug DSLs. (On/Off/No DSL:1/0/-)

DSL 0 --> 31

1 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Here is config:

pompeychimes Mon, 07/06/2009 - 18:47
User Badges:
  • Bronze, 100 points or more

That config did me in. I gotta go to bed now.

shillyar Mon, 07/06/2009 - 17:06
User Badges:
  • Cisco Employee,


I wasnt expecting to see so much going on with dialers.

Forget about adding the deny ip any host as you already have deny ip any any.

Capture just debug dialer and debug isdn q931.when the dialer starts dialing when it not suppose to. We dont need events turned on.

In the debugs you will see a source and desnt ip address. When this dials also gather sh ip ro to the desntination.

Because you have so much going on with your dialers as we really need to know what is trigger the dialer and see which dialer is getting invoke and then figuring out whats wrong.Th

The Isdn line could also be keep up from the remote side so we need to narrow this way down as to what is is triggering this, source and dest, and which dialers are comming up.

Has this ever worked ? properly ?

Also gather sh dialer in about 30 sec intervals 4x.

Thx Steve

Kevin Melton Tue, 07/07/2009 - 06:20
User Badges:


Thanks for working with us on this issue. This configuration has worked most of the time. We did start having issues several months back with the repetitive dialing against only some of the dialer strings. On the most recent bill from the provider, there are 3 numbers that are being dialed over and over again on certain dates.

I am going to follow your recommendations from your last post and try to collect that data.

I have also pulled the formerly published config, as the gentleman later in the chain was correct in that I should not have published the configuration with the dialer strings exposed.

I can re-send this to you if you send me your email address.

once again, thanks for your help.

shillyar Tue, 07/07/2009 - 06:32
User Badges:
  • Cisco Employee,


I tought about that and it was a dumb request on my part im just so used to jusy asking for that. My email is [email protected] email me and let me know which 3 dial strings are showing up all the time and debug dialer will give us the exact source and dest doing the triggering,

What's proably happening is you have some rogure traffic that need to be denyed from being interesting.

Thx Steve


This Discussion