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I want to connect 2 (or more) Windows XP computers from different networks to a mutual virtual network. Also I have a VPS with a modern linux distribution with a public IP. I want to install some VPN software on both clients (Windows XP PC) and the server (VPS).

I've tried installing IPSec server on the VPS, but the problem is that I've faced with config editing in order to use obsolete cryptographic algorithms on the VPS. Also I've managed to run the VPN using older versions of the OpenVPN. But the network wasn't stable, sometimes the connection inside the tunnel could disrupt.

Do you know some Windows XP software that I will be able to install in 10 years from a .msi file? Maybe there are existed some software which creates VPN tunnel using one port SSH-forwarding (using Putty for example). Another idea was using some hardware solutions, for example I could buy 2 mikrotik routers and connect them to the VPN using the modern versions of the protocols.

In past I remember I was using hamachi. But I'm not sure if it's still supporting Windows XP and it depends on hamachi's servers.

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  • Is hardware a relic as well or is running on bare-metal required? Because hiding XP inside VM on some Linux might be easiest/safest combo. Alternatively router or a bridge PC as a CPN entry point should work, but thats a tad bothersome.
    – PTwr
    Dec 24 '21 at 22:08
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    "Able to install in 10 years"... This is a unfulfillable requirement. Create a vpn box instead and let the XP boxes connect normally to that and transparently to them use the VPN. Dec 24 '21 at 22:16
  • @ThorbjørnRavnAndersen I think the vpn box could be more appropriated solution (did you mean using some other devices like routers with VPN support?), because it would be much simpler to connect my old PCs using Ethernet cable instead of trying installing old software on old PCs and the new VPS.
    – Ivan
    Dec 25 '21 at 9:00
  • @PTwr I would like to use my old laptops (so it's bare-metal). And in some cases old games don't work well inside the Virtual Machine. What is CPN?
    – Ivan
    Dec 25 '21 at 9:02
  • @Ivan CPN is a typo in VPN and I can't edit comment because its too old :)
    – PTwr
    Dec 25 '21 at 9:59
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The question is just barely retrocomputing. Windows XP is still used in production here and there. Contrary to the popular beleif, it can be used securely as of 2021 (provided some preparation and that one does not do stupid things) and it is still partially supported by Microsoft (Windows Defender still updates as of few months ago).

openvpn 2.4.18 (the last one to support XP, still somewhat supported by openvpn authors, it is not known to contain grave bugs) is perfectly capable to do what you want, but you need to know what you are doing.

The first thing to consider is that your VPN cannot be faster or more reliable than the Internet connection it runs over. On the other hand, it can easilly become a great deal less reliable and much slower. A misconfigured openvpn is good at both.

If your use case is not tolerant to packet loss or network delays, the VPN can not improve this.

A thing to avoid at all cost: running openvpn over TCP. Use UDP instead. See here. SSH based hacks that you talk about suffer from pretty much the same problem.

A thing to skip because of unnecessary complexity: PKI and certificates. If you really need only 2 computers to connect, use static keys.

A thing that may simplify your setup: use TAP mode. TUN mode in openvpn 2.4 on windows is tricky anyway and you will need two openvpn instances at the VPS

A thing to consider: in 10 years from now the signing certificates of any MSI would have expired. You will need to override the security warnings in order to install it. You may change your computer's date in order to see what happens.

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