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I recently purchased and configured a Raspberry Pi 4 as small home server. Nothing serious, just a little toy to see what I can learn and do on my own. Since I wasn't comfortable with opening a lot of ports on my gateway, I decided to configure a VPN server with OpenVPN and then use the tunnel to do all SSH and other stuff. Didn't know much about before, but after a couple of days I was able to connect. Now I can connect to my home LAN through the VPN tunnel, from most outside locations.

As clients I'm using both my Ubuntu laptop and my Android smartphone. What I'm not able to do is reach the home LAN from my Institution LAN. OpenVPN just can't establish any connection. I've also tried pinging my public IP with no success. (Don't know if it's related, but the reverse tunnel is possible, since a VPN service is available for employees)

What I'm able to do is use the RealVNC client to connect to the native RealVNC server of the Raspberry board. I guess is using some other protocol (HTTPS probably) but I'm not expert enough to understand everything correctly.

I guess my Institution gateway blocks or filters most of outgoing connections, but I cannot understand if it's a matter of ports alone or protocols.

How can I get a correct picture of the situation?

Of course tunneling to outside networks may be restricted for security reasons, but if it's not the case, is there any workaround? In the future I'd like to setup a media server for backups and stuff, so direct connection from my workplace would be nice.

EDIT:
Turns out I made my considerations based on the results of nmap, which were not as reliable as I (naively) thought.
In reality, the random high port which I chose at the beginning for my VPN server was closed for some reason, but the standard OpenVPN 1194/udp was indeed open (even if flagged as closed or filtered by nmap). This might mean that perhaps no policy against VPN tunneling is enforced.
I will try to get more information on this, but at least problem technically solved.

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Firewall, Proxy, based on IP, protocol, port, who knows... there could be all kinds of measures in place.

Outgoing connections are usually blocked for a reason. Granted it might be a stupid reason but still, you might make yourself liable if you use a "workaround". If you don't know how to get around security systems by yourself you probable shouldn't. Or at least don't ask so plainly about it in a public forum.

I would suggest: check with the IT department if they allow for outgoing VPN connection, if the do you'll get an answer from them.

Note: RealVNC has different security issues then a VPN connection so there might be a reason why the allow one but not the other

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  • Thanks for sharing your thoughts. Indeed, I was more focused on the technical problem itself rather than possible motivations behind such a configuration or consequences of workarounds. Now I can easily see at least a couple of reasons why they would want to block outgoing connections like a VPN tunnel. Never wanted to do anything inconvenient, either... just wanted to be sure there wasn't anything trivial for someone with some networking skills. Will try with the IT guys, maybe...
    – adironco
    Commented Oct 5, 2020 at 22:40

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