How can I force a computer to go through the internet to talk to another computer on the same network?

Question

Here is the scenario. I have a server appliance that is distributed to my clients (I'll refer to this as the 'appliance'). The appliance talks to my server to get updates. This is a pretty standard setup. For quality control I want to set up a test appliance at my location that will talk to my server through the internet. It is absolutely crucial that this goes through the internet to make sure the test environment is as close to the production environment as possible.

The simple solution is to get two internet connections, one for the appliance and the other for the server. Is there a way to do this with one internet connection?

Answer 1

If the server is publically accessible already, it should be as simple as using the server's public name or IP on the test machine, assuming you haven't setup your internal machines to know "shortcuts" to your own public IPs (which doesn't make a lot of sense).

Otherwise, you've two options aside from the VPN which someone else suggested:

1. Setup a (http or socks5) proxy on a remote server and set the test machine to use it. This will have the benefit of also testing proxy setups, which are common in organisations.

2. Or, just set up a static route on both the server and the test machine that go through some remote router.

In both cases, firewall and/or otherwise limit the remote machine/router so it can't be used by joe public.

Answer 2

Not really. The closest you can do is to go from this:

Appliance > Server

to:

Appliance > Router > Server

What will happen is if you force your appliance to contact it 'over the internet', the default gateway on the appliance will send the packets to the router. The router will then go "Whoah Nelly! This is actually the IP Address on my WAN port, so I'll just send it back into the LAN segment after matching any port forwarding rules".

If you could get the router to forget about its WAN address (let's say you have two IP's and the router is not aware of the other one), it will get to the first hop of your ISP and immediately come straight back. And then be ignored by your router because it's not aware of it.

That said, pushing the traffic to the router and have the router re-direct it back into your network is probably a pretty good test for everything except for latency and reliability. So it's not really a very good test at all actually because those are the two most important things, apart from port forwarding the right access.

Answer 3

Site to site VPN is what you're looking for. Otherwise, you may look at forwarding ports in your firewall to match the service you're looking to provide to "the other end"..

Answer 4

Your computer already goes through the internet to talk to a computer on the same network. This is the way an internet works. Packets are routed according to routing tables, if they can be routed directly, they are.

Strictly speaking, if you want to impose a less direct route, you can do so by adding a more specific, less direct route to your hosts. But that's inefficient and adds a point of failure.