I’m planning to virtualize a FreePBX 17 system that currently uses an A104DE T1 card. Can I use PCI passthrough to give the virtual machine direct access to the T1 card, or are there compatibility issues I should be aware of? Any experience with this specific setup would be appreciated.
Howdy! Welcome to the forums.
Running Sangoma telephony cards in virtualized environments is not currently supported. Please see:
I haven’t tried it but I couldn’t see why it wouldn’t work - especially if you are passing the entire PCI bus through. I do the same with a graphics card to a server in my homelab and have no problems.. but as Chris said it’s not supported so don’t expect any support from Sangoma.
That is what I was thinking. I know that passing the PCI bus through in Proxmox is fairly easy, and is used for running local LLMs and remote gaming. So I would think it would be possible in theory with no issues.
Our system for the past 10 years was a custom built old Dell Server(not supported) anyway. 
Let us know how it goes! In my opinion sangoma support for physical PBX is nice, but the price is a big ask.
Yes, we are in the same boat. Absolutely not in the budget with all the increasing costs.
UPDATE:
FreePBX 17 has been installed on a Proxmox 9 (Dell R630) Host. The client VM has PCI passthrough of an A102 DAHDI card.
PCI Device is configured and recognized by Debian and FreePBX per the FreePBX 17 install instructions. Today successfully tested hooking up the T1, configuring DAHDI in FreePBX and making a test call inbound. This was a major success and worked flawlessly.
Next test will be to make calls out. But will need to program a soft phone to connect to this server, as the original is still online and on the same network.