Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

simple isdn question

I tried configuring an isdn wan connection recently and after inputting all the necessary data such as the isdn switch type, dialer list, the ip adds. of both bri0 interfaces and then manually mapping the ip adds to the corresponding telephone nos., the bri0 int would come up on both layers 2 and 3 however, when i check the interfaces i would discover two subinterfaces under bri0 which is bri0:1 and bri0:2 and both are down. Do i have to do any configuration on these bri0 subinterfaces. I've been checking my books and other info on the web and there's nothing there indicating such.

I would appreciate any info regarding this. Thanks.

Hall of Fame Super Gold

Re: simple isdn question


these are not subinterfaces but channelized interfaces as the ":" separator indicates. That is, the two B channels of ISDN BRI.

Since the BRI is a dialer interface and not permanent connections you do not configure them directly. But you will see them go up and update the normal counters when active.

Hope this helps, please rate post if it does!

New Member

Re: simple isdn question

Is it possible that the bri0 int could be up on both layers 1 and 2 but its corresponding channels bri0:1 and bri0:2 be down? In this case, i am unable to ping the remote router with a mutual isdn connection. Checking the remote router the same set of info applies as stated above.

Re: simple isdn question


You can check out for dialer interface configs which could be helpful to achieve the kinda policies you want to apply to each locations.

You map each individual dialer interfaces to each locations for granular policy enforcement for the locations..

AFAIK the number would be the same but the policies like AAA or other features may be on individual location specific.


Hall of Fame Super Silver

Re: simple isdn question


Yes it is possible that the bri0 int could be up on both layers 1 and 2 but its corresponding channels bri0:1 and bri0:2 be down. This is the normal case when there is not an active ISDN call in progress.

If you can not ping to the other router with ISDN interface, then there is likely some problem in your config. If you post the config we we have a much better chance to identify the problem. In my experience one of the most common problems that produce symptoms like you describe is that the router does not have a dialer group or dialer list which identifies the proper interesting traffic for ISDN.

So post your config and let us take a look.