Hardware requirements SMB setup

Hi all,

I have no experience whatsoever with FreePBX, but I do have experience in:

  • networking
  • seting up linux
  • building servers

I’m living in Belgium. I love the features offered by FreePBX, at least what I read about them.

I’m facing the task of replacing a traditional SMB PBX connected with the telco with 4 (Euro)ISDN lines, and on the other side with 15 users (I believe this is commonly called “extensions”), and two analoge lines, one with fax device, and another is a doorphone. Additionally, the current digital phones will be replaced with IP phones.

I understand that I must install FreePBX on a server. But, my question is how to interface that host with the ISDN BRI interfaces? What kind of hardware do I need exactly for the above requirements?

You need an ISDN interface card or a router with ISDN voice interfaces that support SIP (such as the Cisco multiservice routers).

There are many manufacturers of telco interface cards for Asterisk. Digium and Sangoma are two large players. Openvox also has a great line of value priced cards.

So basically, all I need is a suitable ISDN interface card of one of those manufacturers. I can just plug it in into any server with a compatible PCI(-e) slot, and FreePBX/Asterisk will recognize it, or is there more to it?

There is a little more to it than that.

I would suggest reading up on Asterisk and DAHDI drivers.

Many of the articles are out of date and FreePBX has a new DAHDI module on the way that will simplify the process.


Hello, basically I’m in a situation very similar to your one and, even if I’m italian, the PSTN BRI interfaces are quite the same (Euro ISDN BRI Point to Point or Point to Multi-Point generally speaking).

Instead of replacing a legacy PBX (like Siemens Hicom/HiPath, Alcatel OmniPCX Office or similar ones) I have to replace a old Asterisk server with very cheap Grandstream IP terminals and with very common and cheap HFC Cologne Chip based single port ISDN PCI Cards (two).

IMHO you should pay a lot of attention about the type and brand of the multi-ports ISDN PCI Card (or Cards, if many single/dual BRI ports are preferred to one single four ports) you’re planning to install on your system.

I state this because there are some inconsistencies about DAHDi Configuration Module (the user part) between distros (supposing you’re evaluating Distros like FreePBX Distro, Elastix or AsteriskNow, just to say).

Another way to solve the ISDN Cards doubts could be to change the scenario and use an external multi-port ISDN/SIP Media Gateway - AudioCodes or Patton are famous and there is a lot of documentation about how connect and configure Asterisk with them - and let the Asterisk server performs IP Trunks to that Gateway thus splitting the VoIP Server from the PSTN interfaces.

But the above one is, by far, probably (even if I really don’t know how much a four ports ISDN PCI Card could actually costs) more expensive.

As said my scenario is very similar: I’ve to replace a system actually connected to 2 BRI (Point to Multi-Point) ISDN NT boxes.

Both these two NT boxes provide also 2 Analog derived lines (used to provide FAX DID) which, IMO, is a superseded way to manage FAXes because each NT could directly provide G.3 FAX service over both ISDN (S0) channels (in Italy you can setup the NT box to manage DID numbers and route incoming calls to the digital side or analog side of the Network Terminator box).

I tested FreePBX Distro 3.211 and 2.210 with DAHDi 2.6.1 and the respective updated DAHDi Configuration Module (user side), then I tested Elastix 2.4.0 RC2 (DAHDI 2.6.1-4) and 3.0.0 Alpha, finally AsteriskNow 2.0.2. All 64 bit editions, all distros updated using scripts or yum command.

The result is that only Elastix 2.4.0 RC2 was able to recognize (at user level) the HFC Cologne Chip ISDN PCI Card, with the others was impossible or, to better explain, was impossible to manage (AKA: setup up the BRI signalling, as example) the digital hardware which, on the contrary, was recognized (kernel modules side) by all the four Distros tested.

At the end this means that I was able to perform and receive ISDN calls with Elastix 2.4.0 RC2 simply performing a manual detect of installed Hardware (through the web user interface) and setting up an incoming route to an extension. With FreePBX Distros and AsteriskNOW was definitely not possible.

That’s very strange (DADHi and Zaphfc modules were OK on all four Distros…) and made me think the task of ISDN Hardware configuration (not detection! which worked at kernel and user space levels) is the MOST important to check. I say this generally speaking because I saw that Voice Mail and basic internal calls were OK.

So…keep your eyes wide open on the relationship among DAHDi Configuration Module used by the Distro (if any) you will chose and the type of ISDN BRI PCI Card you’re evaluating.

Read (just for reference, it’s only my very specific point of view) this thread I opened few days ago and the consequent Feature Request I felt to write down (more important is the general answer I received which make me things a lot about how the BRI Cards were “forgotten during the game”)

I really like FreePBX Distro (more than Elastix, really); it is very well designed and it has a very clear and rich (but simple) GUI, it’s very well supported and it has serious roadmap but, in my case, the Go/No-Go test point is strictly related to have a very smooth and reliable hardware management even if I use a cheap (but very famous and with a very long presence on the market, at least since 2001) BRI ISDN PCI Card Cologne Chip based.

Best regards, Davide.

A few things to keep in mind with regard to the other distro’s you mentioned.

Asterisknow is really broken, many things don’t work out of the box and they are not distributing the latest FreePBX with access to app store.

Elastix is a fork of FreePBX and is not supported by the community.

You left off PBX in a Flash. This is the only other distro offering a complete and current FreePBX experience.

I agree with you about the different experience’s level and freedom that each of the mentioned Distributions is able to provide. I saw those difference testing them on a real machine. I really disliked AsteriskNOW and Elastix (straightforward on BRI ISDN Hardware recognition side) make me feel a little bit too wrapped in comparison to FreePBX Distro.

I’m for FreePBX Distro, definitely.

The only thing I don’t understand about FreePBX Distro is why the DAHDi Configuration Module, at least for what I saw, was not able to manage a simple and well known one port HFC based ISDN BRI Card (pay attention on the fact that the “+” sign on “zaphfc+” showed me that zaphfc module was correctly loaded on each system I tried: FreePBX Distro 2.210.62/3.211.63, on Elastix 2.4.0 and on AsteriskNOW 2.0.2).

Maybe the true question is (at the moment): could we configure and manage a BRI Card recognized by the Kernel only by manually modifying DAHDi configuration files (as reported in many guides) and forgetting to use the DAHDi Configuration Module inside FreePBX ? Is it mandatory ?

Regarding other Distros I cited them only to show that a very specific component (DAHDi Configuration Module) acts in different ways even if, at low level (kernel module and dahdi tools), a common card ISDN Card was recognized and loaded in quite the same way.

Then probably there is another factor to complete the scenario: probably the DAHDi module was developed mainly to satisfy a USA-Centric market (where T1 30B+D trunk is more popular that in Europe, at least among Small Medium Business companies OR where analog trunks are still popular). In Europe (and for sure in Italy) the SMB market relies on BRI (Euro ISDN 2B+D) to connect to PSTN and almost every company has one or more BRI NT (PP/PMP) in use with at least 2 numbers for each BRI (generally the master one used for Voice and the secondary one for FAX if the customer has a FAX machine).

Well the DAHDI module is brand new and none of the developers have access to the type of hardware in question. We really need someone in the EU that understands DAHDI

I would guess it is actually a CentOS and not a DAHDI module issue. If it is an issue of adding a variable to the module we just need to know what it is.

Zap is fully deprecated so it has nothing to do with the conversation.

I don’t want to hijack the original thread (“Hardware requirements SMB setup”) more than I did before but I don’t think (or guess) that could be only a OS (CentOS) issue: almost all above named Distros rely on CentOS (5.8/5.9/6.2 or 6.3) so at low level (dahdi 2.6.1 package / Kernel driver: vzaphfc 1.42 which isn’t deprecated at all) there are some similarities (if someone wants I could post diff of each important command about dahdi: FreePBX vs Elastix as example). The issues begins at higher level on DAHDI Module (lacks of Euro ISDN BRI support, neither BRI Cards tested nor certified, no matter if Sangoma or Digium).

So test, test and test again…before going at customer site (IP phones are not a problem, system Hardware itself is not a problem if you have a good knowledge of Linux and its system administration’s golden rules).