Configuring an IAX Softphone

A major advantage of using the IAX2 protocol is that it is designed to be more friendly to working within odd network configurations, especially working behind NAT. This makes it a fantastic protocol for softphone clients since they are often utilized on laptops that roam into many different networks, often with no control of the network itself (such as when traveling between hotel networks).

The Inter-Asterisk eXchange (IAX) protocol is usually used for server-to-server communication; more hard phones are available that talk SIP. However, there are several softphones that support the IAX protocol, and work is progressing on several fronts for hard phone support in firmware. The primary difference between the IAX and SIP protocols is the way media (your voice) is passed between endpoints.

With SIP, the RTP (media) traffic is passed using different ports than those used by the signaling methods. For example, Asterisk receives the signaling of SIP on port 5060 and the RTP (media) traffic on ports 10,000 through 20,000 by default. The IAX protocol differs in that both the signaling and media traffic are passed via a single port: 4569. An advantage to this approach is that the IAX protocol tends to be better suited to topologies involving NAT.

There exist many IAX-based softphones, but not so many hardware based phones. The most pronounced reason is because IAX2 is not yet an IETF standard, yet many people have become early adopters and have reaped the benefits.

An excellent IAX2 softphone is idefisk, available at[69] for free download. The authors have had excellent results with this softphone, and since it runs on Microsoft Windows, Mac OS X, and Linux, it is an excellent cross-platform softphone to write about. We will be demonstrating version 1.31 in this book, although version 2.0 was recently released (April 2007) but is not yet available for Linux.

Configuring the Channel Configuration File (iax.conf)

Like the rest of this chapter, we’re attempting to get you up and running quickly with the smallest configuration file set possible in order to minimize the problems you may have in configuring your devices. Just like the sip.conf file, iax.conf requires only a few simple lines to get our IAX phone registered to Asterisk. Let’s take a look:



Yes, really, that’s all you need to get your softphone up and running. It’s not the most secure or feature-rich configuration (we’re not even using a password), but this will work.

In the [general] section of our iax.conf file, we have a single option: autokill= yes. We use this option to avoid things from stalling when a peer does not ACK (reply) to our NEW packet (new call setup request) within 2000 milliseconds. Instead of the reply to value yes, you can set this to the number of milliseconds to wait for the ACK to our NEW packet. You can control the autokill option for each individual peer by defining qualify for those peers that you know may be on poor network connections.

The rest of the file contains the definition for our softphone. We define the type as friend, which tells Asterisk we will send calls to this device and also accept calls from this device. A friend is a shortcut for defining a separate peer (send calls to the softphone), and user (accept calls from the softphone). We could also have defined individual definitions for the peer and user like so:



Once you’ve configured your iax.conf file, save the file and reload the IAX2 channel module from your Asterisk console with module reload Confirm your new peer exists by running iax2 show peers.

localhost*CLI> iax2 show peers
Name/Username    Host                 Mask             Port          Status    
idefisk          (Unspecified)   (D)  0             Unmonitored
1 iax2 peers [0 online, 0 offline, 1 unmonitored]

Configure the Softphone

Once you’ve installed the idefisk softphone, open up the client and you’ll see the main screen shown in Figure 4.6, “idefisk”.

[PROD: fileref for Figure 4.6, “idefisk” was out of sequence (pointing to ast2_0405.pdf|png); I changed it to ast2_0406.pdf|png—DCPS]

Figure 4.6. idefisk


After we’ve started the softphone, we need to configure our softphone so we can place calls. We also need to register to Asterisk so we can receive calls. To do this, Right-click on the icon in the top-left corner of the screen, which will open a drop-down menu. Select Account Options from the drop-down, which will bring up the screen shown in Figure 4.7, “idefisk Account Options screen”.

[PROD: fileref for Figure 4.7, “idefisk Account Options screen” was out of sequence (pointing to ast2_0406.pdf|png); I changed it to ast2_0407.pdf|png—DCPS]

Figure 4.7. idefisk Account Options screen

idefisk Account Options screen

Start by creating a new account on the softphone by clicking the New button and filling out the relevant information. The Host should point to the IP address or domain name of your Asterisk system, with the username matching that of the value located between the square brackets [ ] in your iax.conf file. Leave the password field blank, as we did not configure a secret in iax.conf, and the Caller ID and Number can be set to whatever you wish. If you want idefisk to register this account on startup, select the “Register on startup” checkbox. When done, click the OK button to save the new account.

If you clicked the “Register on startup checkbox,” then the phone will attempt to register to Asterisk. On the Asterisk console you will see output telling you that the phone has registered:

-- Registered IAX2 'idefisk' (UNAUTHENTICATED) at

You can verify your registration with the iax2 show peers command at the Asterisk console:

localhost*CLI> iax2 show peers
Name/Username    Host                 Mask             Port          Status    
idefisk       (D)  32771         Unmonitored
1 iax2 peers [0 online, 0 offline, 1 unmonitored]

Configuring the Dialplan for Testing

One final thing to do is confirm dialing through our phone by configuring a simple dialplan in extensions.conf. You can simply test that you have audio in both directions by calling extension 500, or you can modify the dialplan we created in the the section called “Setting Up the Dialplan for Some Test Calls”” section of this chapter to place some test calls. If you also configured a SIP phone at extension 1000 in the previous sections, then the following will not overlap with that, as we’ll be using extension 1001 (unless you configured multiple SIP extensions, in which case just configure a unique extension number for your IAX2 softphone):



exten => s,1,Verbose(1|Unrouted call handler)
exten => s,n,Answer()
exten => s,n,Wait(1)
exten => s,n,Playback(tt-weasels)
exten => s,n,Hangup()


exten => 500,1,Verbose(1|Echo test application)
exten => 500,n,Echo()
exten => 500,n,Hangup()

exten => 1001,1,Verbose(1|Extension 1000)
exten => 1001,n,Dial(IAX2/idefisk,30)
exten => 1001,n,Hangup()

include => phones

[69] The Asterisk Guru site is also an excellent source of documentation!