Page 139 - Asterisk™: The Future of Telephony

[globals]
[general]
autofallthrough=yes

[default]
[incoming_calls]
exten => 14165551212,1,NoOp()
exten => 14165551212,n,Dial(SIP/1000,30)
exten => 14165551212,n,Playback(the-party-you-are-calling&is-curntly-unavail)
exten => 14165551212,n,Hangup()
exten => 4165551212,1,Goto(1${EXTEN})

[internal]
[phones]
include => internal

Connecting Two Asterisk Boxes Together via IAX

Often it is desirable to connect two physical Asterisk boxes together via IAX in order
to send calls between two physical locations (the distance between these locations may
be centimeters or kilometers). One of the advantages to using the IAX protocol to do
this is a feature called trunking, which utilizes a method of sending the voice data for
multiple calls at once with a single header. This has little effect on only one or two
simultaneous calls, but if you are sending tens or hundreds of calls between two loca-
tions, the bandwidth savings by utilizing trunking can be tremendous.

Configuring a Local Firewall

If you’re running iptables on the same machine as the Asterisk box, then you can run
the following commands to open port 4569 for the IAX2 protocol. An excellent book
on iptables firewalls is Linux Firewalls by Steve Suehring and Robert Ziegler (Novell
Press).
# iptables -I RH-Firewall-1-INPUT -p udp --dport 4569 -j ACCEPT
# service iptables save
Be aware that this will allow all UDP traffic from any source access to port 4569.

You will need a timing interface installed on your system, whether it be
hardware from Digium or via the kernel by using the ztdummy driver.
This will require you to have Zaptel installed on your system and run-
ning. See Chapter 3 for more information about installing Zaptel.

Connecting Two Asterisk Boxes Together via IAX | 111