Asterisk Noob - ISDN issues

Hi there,

I have installed asterisk off the ISO image, and so far it is working pretty good. But only for internal use. I have softphones on all my PC’s on the lan, and the telephony side of things are working great

I have now added a PCI ISDN card, and I am not sure if it is recognized in the system.

How can I see if it is installed, and where do I tie in the ISDN4Linux package?


At a guess I’m assuming that you are using BRI (Basic Rate Interface - 1 D channel & 2 B channels)?

Ok first thing first. Check if kernel has seen the card. do this by typing dmesg (or dmesg|less) and look for you card. Alternative you can use lspci.

You have a number of options in asterisk for using BRI cards.

  1. ZapHFC - assuming that you have a card with a Cologne HFC chip on it (to find out look at the chip on the card or look at the output from dmesg)
  2. Capi with chan_capi - this will in all likelihood require you to recompile the linux kernel for Capi. Obviously you need a supported card
  3. mISDN (modular ISDN) with cha_misdn - even more complex. You will need to patch then recompile the kernel.
  4. i4l (ISDN4Linux) - is dead (well depreciated) in the 2.6 Kernel tree

The first option is the simplest, and I’ve found it to be quite reliable. I have a asterisk server currently running with 2 HFC cards, and I haven’t had a problem so far (ok it’s only been up for 4 weeks).

For future reference. Include the relevent info in you posts:
What version of linux (and I mean the kernel)?
What distribution (it helps people know where to find things)?
What version of Asterisk?
As you post mentions hardware, what hardware?

Good luck.


These are the specs on the machine…

Kernel 2.4.21-37.EL

ISDN card: 00:07.0 Network controller: Cologne Chip Designs GmbH ISDN network
controller [HFC-PCI] (rev 02)

I installed asterisk off the asteriskathome ISO image from the Digium website and it is Asterisk 1.0.9.

When I do a lsmod however, it does not give me anything regqarding a ISDN card.


Well to start with I have admit that I don’t know A@H very well (I played with it for a couple of hours). It’s based on CentOS which is really a derivative of RH EL. I haven’t used RH in about 8 years.

The good news is that you have the right ISDN chipset. (Cologne HFC) and it look like you kernel has detect it.

AFAIK A@H doesn’t have the kernel ISDN modules compiled, I stand to be corrected. So that excludes the chan_misdn and chan_capi Asterisk setups. However, I’mI pretty sure that A@H is compiled with BRIStuff (no sure exactly which version). You can check easily by look for the zaphfc.o (or zaphfc.ko) in the /lib/modules/2.4.21… directory or normally when you are in the Asterisk console there will be some rubbish about BRIStuff.

The following links are a good reference on how to configure the zaphfc drivers:

A couple of tips (to avoid future problems):

  1. If you have audio problems make sure your ISDN card isn’t sharing an IRQ with another card
  2. zaphfc wouldn’t load with ztdummy, you must remove ztdummy
  3. ztcfg can only be run once after reboot.