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Asterisk Support Pages

Asterisk is under continuous development. When we perform a customer implemenatation, we choose a stable release from the active development stream. For people who like to get their hands dirty with tuning Asterisk, we offer the following hard won nuggets of knowledge gleaned from the smart contributors of the Asterisk mailing lists.

Comments below are based upon a Redhat 9 system with minimum of 2.4.20-19.9 kernel. As of October 1, Asterisk should now be stable on this platform.

Disclaimer: I havn't tried everything mentioned here, so caveat emptor.

Where did Asterisk originate?

Mark Spencer at Digium started the development of Asterisk as an add-on solution for the range of telephony cards the company offers.


In the mailing lists, you may see Asterisk written simply as '*'.

Searching for Information

Use Google to search for information regarding Asterisk. To search the Asterisk mailing lists specifically, use ' yoursearchwordshere'.

Channel Banks

Channel banks separate digital T1 lines into individual analog lines. Ports that you can plug an analog phone into are FXS ports, and ports you connect lines from the Telco into are FXO ports.

Some Cool Asterisk Tricks

  • Using the Digium T1 cards and running both voice and data across a single link.
  • Sharing dialling plans between offices by using the IAX2 trunking feature
  • Using AGI scripting to add custom functionality

Codec bandwidth utilization over a trunking channel:

Codec Bandwidth

IAX2 & Register Hints

A register directive is only required when one of the servers has a dynamic IP address which cannot be resolved from the outside or is behind NAT. The entry on the destination server needs to have "host=dynamic".

A "type=peer" registers with a "type=user" or "type=friend".

IAX2 port is 4569. IAX port is 5036.

Call Pickup

Use *8 to pick up an extension.

in sip.conf, callgroup and pickupgroup are necessary:


Installation hints (without Digium cards)

Our version of the Redhat KickStart File can be used to prepare a minimal Linux installation. See Redhat's KickStart Configuration Guide for more information on how to use this file. It is a good idea NOT to install X-Windows, a server type of install is best.

Make sure you have the following libraries and programs installed:

  • libtermcap-devel (may no longer be needed)
  • ncurses-devel
  • readline-devel (may no longer be needed)
  • openssl-devel
  • postgresql-devel (for cdr records)
  • bison (may no longer be needed)
  • newt (may no longer be needed)
  • doxygen
  • zlib-devel
  • kernel source (may no longer be needed)

Obtain the latest version of Asterisk:

  • cd /usr/src
  • mkdir digium
  • cd digium
  • svn checkout asterisk
  • svn checkout zaptel
  • svn checkout libpri

Build the low level drivers

  • cd /usr/src/digium/zaptel
  • edit Makefile and remove the '#' before ztdummy on line 90 if a 2.4 kernel
  • make clean
  • make install
  • make config
  • service zaptel start|reload|restart

Build the remaining directories

  • cd ../libpri
  • make install
  • cd ../asterisk
  • make install
  • make samples
  • make progdocs

Configuration files have been created in /etc/asterisk.

To start, run 'asterisk'. To load automatically, put into your /etc/rc.d/rc.local file:

  • modprobe ztdummy
  • safe_asterisk

Music On Hold

Music On Hold requires MPG. The file that comes with Redhat does not work correctly. To obtain a workable solution, these steps may help.

# cd /usr/src
# wget
Extract it and compile:
# tar -zxvf mpg123-0.59r.tar.gz
# cd  mpg123-0.59r
# make linux
# make install

once compiled make sure there is a copy in /usr/bin/mpg123

remove symlink to mpg321. then
# cp /usr/local/bin/mpg123 /usr/bin

Update Asterisk from CVS

In each of the three subdirectories, zaptel, libpri, and asterisk, run the following commands (these commands are obsolete, I have to revise this as SVN is now used):

  • make clean
  • cvs update
  • make
  • make install

An alternative for the asterisk directory (the preferred way as it updates the date in Asterisk's sign on banner):

  • make clean
  • make update #which automatically connects to CVS
  • make install

A message on Oct 24, 2003 indicated that there's a tiny bug around: the current installer forgets to copy "hours.gsm" to the sounds/digits directory. If you use this in your voicemail.conf then vm will just hang up on you when it gets to say "hours"...

Be sure to backup /etc/asterisk and /var/lib/asterisk/sounds before performing an update.

Digium G.729 license issue

Asterisk has an autostart script which would be /etc/rc.d/init.d/asterisk. Make the following modification if you are having some problems with getting Asterisk to run.

daemon /usr/sbin/asterisk
daemon screen -d -m asterisk -vvvcng

Someone indicated that "The G729 codec needs a tty. The safe_asterisk script makes sure a tty is available for Asterisk."

Eliminating some internationalization errors:

In /etc/sysconfig/i18n, the first line reads something like LANG="en_US.UTF-8". Change it to read LANG="en_US", and reboot.

Dev Lite Config Notes

ADD TO YOUR rc.local inititialization file:
rmmod usb-uhci
modprobe usb-uhci
modprobe wcfxo
modprobe wcusb
sleep 1
ztcfg -vv
sleep 1

/etc/zaptel.conf should be
loadzone = us

should include something like this:

channel => 1

channel => 2


Some remarks from Rich Adamson regarding the installation, care, and feeding of Festival, the text to speech processor are included in this link.

X-Lite Configuration settings

Under System Settings -> Sip Proxy

  • Enable: yes
  • Username: The name or number in your SIP.CONF [brackets]
  • Authorized User: Leave blank (and remark out in SIP.CONF if you have it in there.)
  • Obviously set the password.
  • Domain/Realm: The Name or IP of your Asterisk box.
  • Sip Proxy: The Name or IP of your Asterisk box.
  • Send Internal IP: ON (If Sip phon and asterisk are on the same network)

AGI Scripting

Manager Interface

Outgoing calls

Locate a file called '' in the asterisk directory. Modify the file to meet your call requirement. Then drop it in /var/spool/asterisk/outgoing. Asterisk will make the call for you.

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