You’ve got a machine hooked up to the Internet via a shiny new cellular modem, which you plan to administer remotely. You do a quick check on the external IP, and try and log in from another PC. Try as you might, SSH simply won’t connect. What gives?

The reality of the modern internet is that most clients no longer get their own unique IPv4 address. There simply aren’t enough to go around anymore. Instead, most telecommunications operators use Carrier Grade Network Address Translation which allows a single external address to be shared by many customers. This can get in the way of direct connection attempts from the outside world. Even if that’s not the case, most cellular operators tend to block inbound connections by default. However, there is a way around this quandary – using a VPN.

A Network That’s Private And Virtual

VPNs, or Virtual Private Networks, are exactly what they sound like. They’re a private network that exists between clients on a broader public network like the Internet. When it comes to making connections to remote hosts on cellular connections, they’re the perfect tool to get the job done. Having the remote host connect to a VPN server gets around the issue of rejected incoming connections, as all traffic goes through the VPN tunnel initiated by the remote host itself. Additionally, it means that other hosts connected to the VPN can talk to the remote host as if it’s another machine on a local network. With the correct setup, a VPN can be a highly secure and flexible way of talking to remote machines with a minimum of fuss and bluster.

You can run your own VPN server at home without much trouble. You’ll need a computer with reliable Internet access, that can accept incoming connections. Typically, this will involve enabling port forwarding on your home router so that connections made to your home IP on a particular port are forwarded to the computer running the VPN server software. Additionally, you’ll need to make sure your home internet connection isn’t behind carrier-grade NAT. Generally, if you’ve got cable, ADSL, or fiber, a simple phone call to your ISP is all that’s required. However, in some cases, you may find you have to upgrade to a higher tier connection package to get such treatment. There’s no need to have a static IP, either; dynamic DNS services can make it easy for your remote system to call back home. You can even run your own Dynamic DNS if you so desire.

So, assuming you’ve got a computer standing by, and a router with an open port to the wider internet, all you need to do is install the right software. OpenVPN is a popular choice for running a VPN server, and has all …read more

Source:: Hackaday