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Create your own Voice-over-IP PBX using Asterisk

By   |  February 21, 2006

Asterisk is already hard at work in South Africa. Its being used as a PABX, for call-recording, for both small and large call-centres, for voice conferencing, and in CTI (Computer Telephony Integration). Its providing inter-office “free” calling, and very inexpensive international calling. In every case, Asterisk-based solutions are a fraction of the cost of the traditional equivalents.

Voice-over-IP (VOIP) is built right in to Asterisk. Connecting into the traditional phone network
is done using interface cards readily available in South Africa, or by connecting into an ITSP (Internet Telephony Service Provider) via VOIP over the Internet.

Asterisk provides all the functions of even the most expensive traditional PABXes simply with software running on an ordinary PC. What’s more it comes with all the open-source goodness that Tectonic readers know and love.

At Connection Telecom we like to say that the coming together of VoIP and the open source world is resulting in the most dramatic change in the world of telephony since we last heard “Nommer Asseblief?” [”Number Please” in Afrikaans].

Finding more information about Asterisk and VOIP
The original home of Asterisk is Digium Inc. Mark Spencer, CEO of Digium, started developing Asterisk to serve his own company’s needs. Since that time, developers from all around the world have been contributing to a project that has just grown and grown. At you’ll find the home of the Asterisk community.

If you are going to be an Asterisk user, its essential to get onto the project mailing lists. You can subscribe at

If you are interested in more general VOIP information, as well as lots of details about Asterisk, you should visit the VOIP Wiki, which you’ll find at

South Africa has its own mailing list for discussing VOIP here in SA – send a mail containing “subscribe voip” to to get signed up. A local Asterisk email list was recently established at

The growth of VOIP has political and regulatory implications too. To read about some of that, start with Jeff Pulver’s blog on

Getting a taste of Asterisk
Asterisk is a product of the “lean and mean” school of application design. Due to the real-time requirements of voice processing, Asterisk is a command line driven application; no GUIs here.

Luckily for those of us that aren’t full-time techies, various projects have sprung up around Asterisk to help make it easier to use.

Two in particular are notable: Firstly, Coalescent Systems in Canada have generously open-sourced their web management interface for Asterisk. As usual this project is now seeing rapid community development. Secondly, the Asterisk@Home project has created a bootable installer that, in just 20 minutes or so, turns a spare PC into an Asterisk system including AMP for easy management.

Note that, notwithstanding the name, Asterisk@Home is a suitable platform for PABX systems up to 100 extensions or so.

All you need to create your own PABX based on Asterisk is a modestly powered PC and the Asterisk@Home install CD. Your Asterisk PABX system is useful even with no additional interface hardware. You can use it with either hardware SIP phones or PCs running software SIP phones. Assuming that your Asterisk PABX is on the Internet, these soft- or hard-phone users can be anywhere in the world.

If you like, you can connect your Asterisk system to other VoIP users and to the ordinary phone world using one or more VoIP service providers. Use one that is based in the UK or the US and suddenly your overseas calls are much cheaper than local calls!

With the addition of a suitable interface board, your Asterisk system can also connect to the traditional telephone world using a local Telkom connection. Boards are available to suit ordinary analogue lines, ISDN basic-rate lines, or even ISDN primary-rates. You’ll find that these interface boards are a fraction of the price of similar boards for traditional proprietary systems.

The resulting system includes AMP (Asterisk Management Platform). AMP provides a web-based configuration interface which allows you to:
– Set up extensions and voicemail mailboxes;
– Setup outgoing trunks using both VOIP links and traditional phone lines;
– Create groups that ring multiple extensions;
– Create IVR (interactive voice response) menu systems;
– Set up call queues;
– Design sophisticated least-cost call routing.

Via the web interface you can also:
– View the status of the system via a live operator panel;
– Manage your voicemail mailbox (including listening to your voicemails or other call recordings);
– View detailed information about the status of your Asterisk system;
– Edit configuration files directly in the Web interface.

Under the covers, Asterisk is very configurable. Especially notable is the very powerful extensions.conf configuration file that allows you to control call handling at a very detailed level.

Asterisk’s feature set is comparable to even high-end proprietary systems: voicemail, call Queueing, call parking, call recording, music-on-hold, interactive-voice-response, text-to-speech conversion, and database integration are a few of the highlights.

I should say that Asterisk is a complex application, running in a complex environment. Asterisk@Home does a good job of packaging up this complexity, but be prepared to invest some learning time if you really want to use all of Asterisk’s power.

Also, please bear in mind that Asterisk is licensed using the GNU Public Licence (GPL). Be sure that you comply with the terms of the GPL as you use Asterisk.

In this article we’ll take you step-by-step through the process of installing Asterisk@Home, and help you connect some soft-phone clients. We’re aiming to get you paddling in the open-source telephony waters, and hoping you’ll join us in deeper waters as you get to know your system better.

Hardware requirements
To run Asterisk@Home you will need a spare PC system that you can dedicate as a PABX. At minimum, your machine will need a 300MHz PII processor, 128MB of RAM and a 4GB hard drive. You’ll also need an Ethernet port.

Faster machines will of course provide more capacity; we’ve found a modern 2GHz or faster processor and 512MB of memory will provide enough power for an office of 50 extensions or so.

Your system will also need a CD-ROM drive from which it can boot.

Asterisk@Home’s installer will wipe out any previous contents of the machine hard drive, with little warning. So don’t use a machine whose contents you need to keep!

Asterisk@Home installation
1) Download and burn your Asterisk@Home Install CDROM

At the time of writing, the latest Asterisk@Home was version 2.4. You can download it at

On Linux, use xcdroast or similar to burn this image to a CD-R. On a Windows system, Nero Burning ROM or similar will do the job.

An important word of warning: On booting, the Asterisk@Home CD proceeds immediately to reformat the system hard drive. So label your CD clearly with a warning not to attempt to boot it! (Or, throw it away after you’ve finished your install.)

2) Boot the Asterisk@Home install CD on your target machine

Insert your Asterisk@Home CD into the target system’s CD-ROM drive, and start the machine. Asterisk@Home’s installer should start. If it doesn’t, check that the machine BIOS is set to attempt to boot first from the CD-ROM.

Press Enter at the prompt.

Asterisk@Home will now proceed to install Linux onto the hard-drive. The previous contents of the hard-drive will be erased.

The installer will then eject the CD-ROM. Take the CD out of the drive and wait whilst the machine reboots.

3) Wait patiently whilst the installer compiles Asterisk

On a slower system it may take up to half an hour for Asterisk to compile. So now would be a great time for a cup of coffee.

When the compile is finished, you’ll see a system login: prompt.

4) Log-in, change the root password

Log in as “root”. The password is “password”:

login: root
Password: password


You should now immediately change the root password. The Asterisk@Home web site warns that systems with the default root password HAVE been hacked!

# passwd
New UNIX password: (type a new password)
Retype new UNIX password: (type the password again)

5) Complete the remaining configuration steps

Note that entering help-aah will give you some help on Asterisk@Home setup scripts.

– Type config to set the system timezone to the local one (I use Africa/Johannesburg”);
– If you need to configure the Ethernet with a static address, type netconfig;
– You should type install-pdf to install pdf support if you expect inbound “system” fax support to work. You will need an Internet connection and a little patience whilst everything needed is downloaded and compiled.

(Continued on page 2)


2 Responses to “Create your own Voice-over-IP PBX using Asterisk”

  1. Italo
    February 25th, 2006 @ 12:00 am

    It\’s a great tutor!
    Thank you to help us!!


  2. Lionel
    March 2nd, 2006 @ 12:00 am


    I have a question :
    I have installed on a server Asterisk Home edition. I want to install Asterisk Business Edition + Linux.
    I have a (bootable) cdrom from signate with Linux and Asterisk on ti. If I try to boot from my CDROM (BIOS settings are set) the server boots from the HDD (Asterisk Home).

    If I put the CD in my laptop and reset, the laptop boots from the CDROM.

    I put in a other cdrom player in the server. Same thing.
    So, does anyone know how i can solve this or what the problem is ?

    Thanks in advance !


    Sounds like a hardware rather than software problem. Try burning the CD at a lower speed, or burning it from the machine you want to install to. Sometimes older CD Rom drives have trouble with disks burnt too fast – ed

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