Interconnecting Asterisk IP PBX
Hi all,
It has been a long time since I had published any item on this blog. There have just been distractions but I am back now. The period of absence does not mean that nothing has been happening in the IP PBX world or that I have not been doing things. I will share with you a scenario where I was involved in the design of a voice network that spans Nigeria and Ghana.
This scenario will make us understand practical situations where we can use an IP PBX and how we can configure the PBX to achieve so much.
- Users in Lagos should dial the extension number of the Accra users directly without a leading number and vice versa.
- The users in both countries to make calls on their respective PSTN lines
- Nigerian users can make PSTN calls on Ghanaian Asterisk and vice versa.
Assumptions and Requirements:
·
All configuration to be done
via FreePBX 2.8.1.4
·
Flavour of Asterisk is Elastix
(Asterisk 1.8.12.0) running on CentOS Linux
·
The asterisk has been properly
installed and working correctly
·
Extensions have been created on
respective PBXs.
·
PSTN cards have been installed
on PCI ports and necessary drivers installed
PSTN Cards that can be used include the following
PSTN Cards that can be used include the following
On the Nigerian Asterisk
1.
An IAX trunk was created to
connect to the Ghanaian Asterisk box.
2.
A route was defined that
ensures that upon dialling a 3 digit number starting with 3 (i.e 3XX), the call
is transferred to the Ghanaian Asterisk via the IAX trunk earlier created.
3.
A PSTN card was installed on
the Asterisk and configured with DAHDI
4.
A Route
was configured that ensures that upon dialling a leading “9….”, the PBX will
select the DAHDI trunk. The Extension 20X in Nigeria will dial 9xxxxx to call
via the PSTN.
On the Ghanaian Asterisk
1.
An IAX trunk was created to
connect to the Asterisk box in Lagos.
2.
A route was defined that
ensures that upon dialling a 3 digit number starting with 2 (i.e 2XX), the call
is transferred to the Asterisk in Lagos via the IAX trunk earlier created.
3.
A PSTN card was installed on
the Asterisk and configured with DAHDI
4.
A Route was configured that ensures that upon dialling a leading “8….”,
the PBX selects the DAHDI trunk. The Extension 30X in Ghana will dial 8xxxxx to
call via the PSTN.
The above configuration achieves the first two
requirements but not Nigerian users making calls via Ghanaian PSTN and vice
versa.
The third requirement can be interpreted as
such:
Lagos user (2XX) dials 8XXXXXXX to call
PSTN in Ghana.
For example, 201
in Lagos wants to call +233 30 238 4000 in Ghana. Instead of making an
international call via its own PSTN trunk by dialling 9 009 233 30 238 4000, he
should dial 8 238 4000 just like a 3XX can in Ghana.
Ghanaian user (3XX) dials 9XXXXX to call
PSTN in Nigeria
An example of this
is, 301 in Accra calls +234 1 271 2400 in Lagos. Instead of making an
international call via its own PSTN trunk by dialling 8 009 234 1 271 2400, he
should dial 9 271 2400 just like a 2XX can in Lagos.
Configuration Solution:
Since an IAX trunk exists already,
therefore, only new routes are to be configured.
On Lagos PBX, configure a route using a
leading number 8 to simply use the predefined IAX trunk to take the call to the
Ghanaian PBX which upon translation will route such a call to the DAHDI trunk.
Similar configuration will be done for the
Accra PBX but for a leading number 9.
Note:
Despite the configuration looking so simple, if the organisation is to route VOIP calls between Nigeria and Ghana, the same set up can be used and it will work effectively. The only difference may be that the hardware will be scaled to accommodate more calls simultaneously.
Next:
We shall be looking at a setup that integrates two different flavours of Asterisk: Elastix (Palo Santo) and SwitchVox (Digium).
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