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Both these two NT boxes provide also 2 Analog derived lines (used to provide FAX DID) which, IMO, is a superseded way to manage FAXes because each NT could directly provide G.3 FAX service over both ISDN (S0) channels (in Italy you can setup the NT box to manage DID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.