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I recently started using OpenVPN. It is useful because you can securely connect many clients from different networks. However, when two clients communicate, they are not directly connected but they go through the server. This means that the performance depends on the server's upload and download speeds. Is there a way for the clients to connect to each other directly, similar to how it is done with Hamachi? I'm basically trying to connect some clients that are behind firewalls so that they can communicate as if they were on the same LAN. I was looking for an Open Source solution where I can host the server that organizes all the clients.

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tinc seems to do the trick :


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In OpenVPN no.

You can certainly create the mesh configuration, but there's no automatic support.

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Hamachi (As I understand it) also goes through servers, they're merely servers owned by hamachi, rather than your servers. If two machines cannot communicate, then they won't be able to open tunnels to each other. If they can, then you can set up the VPNs on each machine, to each other machine to do this. Or, you can host a server somewhere with all the OpenVPN tunnels terminating on it.

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Hamachi claims to have some sort of UDP "hole punching" technology, whereby it persuades both NAT/firewall devices to open tunnels using assistence from the server. I don't know if there is an open source package to do this, but in theory if there were it could be used with OpenVPN. – pjc50 Jul 24 '09 at 8:57
i would guess they use UPnP rather than a STUN server technique... i might be wrong though. – djangofan Jan 15 '10 at 16:51
UPnP isnt supported and enabled on all devices so i dont think this is their solution. Rather i also think its some customized STUN-based technique – Angel Apr 21 '11 at 11:59

The UDP hole punching isn't unique to Hamachi. You might want to start by looking up STUN. (This won't help on its own, you might have to make something if you need it badly enough)

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