Backup Onsite PBX

Hi everyone, I have a question regarding backup onsite pbx… I have a client that would like to have a backup PSTN line but is currently in a hosted PBX environment. That is, I have freepbx running at a datacenter and the DID routes to there. The client has a PSTN line in the office and would like the phone system to continue to work if there a local internet outage. I figure I can install a PBX locally with an FXO port, but how do I get the offsite pbx to route to the PSTN number if it’s unable to reach the phones? Is there a way to get it to act differently if the phones that are part of a ring group are all unavailable?


Each RG will have a destination of no answer field.

Right, but if the phones are up, I want it to go to voicemail. if the phones are not connected I want it to fail over to to the PSTN number.

I would write yourself a custom-context that explores the various RG members with e.g. extension_state([email protected]) and act conditionally on all of them returning 4.

I will likely do this exactly. Thanks for your help :slight_smile:

I would also suggest you revisit your system design , I would replace the FreePBX at the data-center with a real SIP proxy (I use Kamailio) there is no need for PBX functions both locally and at the normal VOIP point of ingress/egress. The P in PBX stands for “Private” and that is what you are asking for, the PSTN’s are Private to the system, let the local PBX mange it and using something more flexible and lighter on it’s feet at the data-center as your VOIP routes to PSTN.

You definitely have to revisit your design.
If you have to go internal PBX, why wouldn’t you route to the internal PBX as the primary PBX?
If the call fails over to the “secondary” as I have labeled it, then you would make the call ring the hard wired line.

I do this a lot with Primary internal and secondary externally.