No Audio when calling extension at remote site

I’ve read the “no audio” prior topics. But unlike those I read I am not running over SIPs; I have a FreePBX server at one location with 3 analogue lines coming in. I have recently leased a second office location and had my IT provider establish a VPN between them.
I am not very techy, so spent a few thousand to get the VPN set up and to configure the Cisco IP phones etc at the remote location. Unfortunately we get the familiar “no audio on calls from an extension” back to the home PBX site. I gather it is a NAT issue, but my IT provider is telling me I should go with their preferred PBX offering Allworx and I am being stubborn I suppose.

Is it possible for me to have a remote site and not need to do anything crazy to get it working. I’d happily pay an expert to call me and capture the required information, because I don’t know how to. I did set up the Free PBX server and all my phones some 5 years ago, and so have my configs, but in terms of my router and network config I am not able to do that.

Here is an email (edited to hide identities) from my IT provider

"Anyway; we got the new routers installed, and applied the specific VPN that Ubiquiti had recommended we try. It unfortunately netted the same result. We also tried adding a regular VPN, and it netted the same result.

As a final “Hail Mary” you can ask your friend what ports need to be forwarded externally, to allow phones to be connected without a VPN………… but if I remember correctly he was against that, AND, we also tried what we could find on the internet for this, and it did not work as well."

And another from old Army friend (referred to above) of mine that is more of a VoIP specialist (unfortunately he lives in Australia and I am in Canada).From my VoIP specialist friend…

_"Although AutoIPsec VTI is a direct VPN connection between each site, it actually doesn’t allow multicast (and other like RTP etc) traffic through the VPN itself. This explains the issues we’ve been having. _

WTF - they have provided you with a solution that doesnt work John. I wouldn’t be paying them for that. "

So, anyone know how I may get this to work, or should I go buy a SIP PBX that can work across multiple sites?

Any assistance would be appreciated. I initiated this project in August 2018!

Hi John,
Let me get this straight you have a freepbx server on one location and you have ipsec tunnel between both sites, the phones at remote site are connected. if you call your voicemail from remote site extentions do you hear voice?
What i can think here is going on is the tunnel is not allowing RTP (Real Time Protocol) UDP port 10000-20000 to go across.

I have same configured a costumer sonicwall firewall bothside ipsec vpn and i have no issue.

Good Luck

If this phone is connecting through VPN, you need to add the remote subnet under SIP Settings.

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Thanks, I’m going to send your suggestions to my IT supplier and also my VoIP friend, they’ll be able to check your suggestions against what they’ve tried. I’ll test the calling voicemail shortly.

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