» posted on Saturday, June 5th, 2010 at 20:38 by Nigel
Going mobile with VoIP and SymVPN
A break (and probably quite a welcome one) from surround sound on Freeview this weekend, with a little more tinkering with the VoIP phone system. One of the theoretical benefits of using a phone system like 3CX is that you can have remote extensions.
Put simply, that means that as long as there’s an internet connection, you can plug in a VoIP phone anywhere, and it will connect to the phone system. So, I could be working in someone’s office, and if there’s an internet connection, I can have my usual phone with me, so when someone calls my business phone number, it would ring wherever I am, anywhere in the world. Of course you can do that with call forwarding, but with VoIP there are no call charges, and you can do things like transfer a call to a different extension too.
Now, it would be a bit tedious to carry a desk phone with me, but my Nokia E72 has VoIP built in, and can connect via WiFi; I’ve used that with previous phones in the past to avoid roaming charges when abroad, and when I’m at home the E72 connects to the 3CX phone system perfectly.
Unfortunately, VoIP is very picky when it comes to firewalls, and unless things are configured properly, you end up with problems like audio only working in one direction – and that’s exactly what I’ve been experiencing when trying to make the E72 work when I’m away from home. I’ve tried the usual solutions, but without being able to alter the settings on some of the networks where I use the phone, it’s hard to be sure it will always work.
Step forward the VPN
Since the phone works perfectly when it’s connected to my home network, a VPN is a potential solution, since it can make the phone look as if it is connected there, and the E72 has a built in VPN client, while my new Draytek broadband router has a VPN server that supports IPSec, PPTP and L2TP.
The standard Nokia client uses IPSec, which is a bit of a pig to configure in my view. It made my head hurt and generally and drove me to distraction, so I opted instead for Telexy’s SymVPN which does PPTP, and has a two week free trial.
That’s much simpler to configure, and it didn’t take very long at all to have the phone connecting to the router, and signing in to the 3CX phone system. Unfortunately, that’s as far as I got – there was still just one way audio. I think that is something to do with address allocation on the Draytek and how it handles public IP addresses – my network doesn’t use NAT. I’m sure it could be fixed given time, but in between other work, I had only three days of the SymVPN trial left.
So, I’ve opted for the alternative – 3CX runs on a Windows XP Professional system, and that can also accept PPTP connections, and having the phone connect directly into the same machine that runs the VoIP software should make it much easier to avoid firewall and routing problems.
And, indeed it did; the only other thing that I needed to do was to disable the VPN service on the router, and add a rule allowing traffic to port 1723 to pass through to the Windows computer, for both TCP and UDP, as well as IP protocol 47, which is something called GRE, and essential for PPTP VPNs.
Given more time, I could probably have solved the issues with the Draytek VPN server, and maybe even made it all work with the standard Nokia VPN, but there are only so many new things I like to learn at the same time.
Once SymVPN is installed, it creates a new access point on the phone. I have a destination configured for my VoIP account which has the home WiFi network first, then the access point from SymVPN.
Within SymVPN, you can pick which access point is used to create the VPN connection; when I tell the phone to sign in to the 3CX system, if it can’t find my home WiFi, it then uses SymVPN and connects that way. To all intents and purposes, it works exactly the same as when I’m at home, whether using another wireless network, or Orange’s data service.
So, I can dial a number on the E72 and press the right hand soft key (labelled ‘Net call’), to call using my home phone line. And calls that come in to my business number will ring on the mobile, wherever I am in the world.
If there’s free WiFi, then it costs me nothing more than it would cost to be using the phone at home – no incoming roaming bills, or international calls back home. People just dial my normal number to reach me.
Even if I can’t find free WiFi, I have an option on my mobile phone called Orange Travel Daily Data, which provides 50MB of data per day when abroad, for £8.50. Even a conservative estimate of how much data VoIP calling uses suggests that that 50MB limit is around 2 hours of calling – which would cost a lot more in roaming charges; the same price would get you around 45 minutes of incoming calls, or just 22 minutes of calls back to the UK.
Now that it all works, I’ll try to find time to do a step by step guide to setting some of this up.
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