There’s a cognitive dissonance that I’d like to talk about. WARNING: Theory stuff…
The FreePBX phone server uses OpenVPN for it’s “phone to server” VPN, but it relies on the calls going through an IP Network. There are lots of examples (here in the forums) of people setting up these services.
The problem with setting them up is that they aren’t “using the iPhone or Android” to make the calls. You have to install a new SIP Phone App on the phone (there are lots out there - some work better than others) that runs on your handheld device. Effectively, the phone becomes two phones - the regular Cell Phone interface and the new SIP Network Connected interface.
Most of the people I’ve talked to (not nerds like us, just regular civilians) don’t understand how that works. “I just want to make a call…” is their call to arms. They don’t want to have two (or more) different ways they can be contacted.
The other issue is that the IP networks that run under most cell phones aren’t really well suited to SIP phone operations. Some carriers deliberately mess with SIP signaling, others just don’t care, so they don’t give you the tools to not use their cell network.
Having said that, there is still some hope. There are several techniques that we can use and help you set up that should get you close to where you want to go.
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You can use a “DISA” phone line. Basically, you dial the number and get a dialtone on the PBX. When coupled with automated “call back” features, this creates a secure, very good connection system that works with any phone (iPhone, Android, Superman Booth, etc.). It gives the user the appearance of being “inside” the network even when outside.
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There is FM/FM (Find Me/Follow Me) which allows you to extend the reach of your extension on the desktop to phones external to your network.
There are actually lots of other ways to help enable your client’s phones without “integrating” them into the network.
So, in addition to the SIP way, there are other ways that work with the native “telephone-ness” of the devices you want to reach out to.
If you’re sure you want to test this out, start by searching the forum for “OpenVPN” and start looking at some of the discussions. One of them should point to a Wiki that gives you some meat that you can then use to make your phones do what you want. For example:
is one thread - there are lots more that go into lots of specific detail about different parts of setting up VPN connections.
I hope this doesn’t like a lot of doom and gloom - the way forward isn’t necessarily simple, but it is doable.