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Asked: 2020-12-16 09:14:32 +0800 CST

Can't connect local network VNC server when OpenVPN client is connected on this server

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Hardware A: Ubuntu 20.04 (192.168.1.61): Installed VNC server and added OpenVPN client config to some remote server C.

Hardware B: MacOS 11.1 (192.168.1.51): standart preinstalled VNC client.

From B to A i have perfect VNC connections when OpenVPN is disconnected. But when connect from A (as client) to OpenVPN server, VNC connection is immediately down. At the same time smb, ping (A <-> B) and traceroute (A <-> B) works perfect and with same behaviour like with disconnected OpenVPN (down only VNC).

From B to A (with and without VPN):

% traceroute 192.168.1.61
traceroute to 192.168.1.61 (192.168.1.61), 64 hops max, 52 byte packets
 1  192.168.1.61 (192.168.1.61)  27.855 ms  2.296 ms  35.563 ms

From A to B (with and without VPN):

$ traceroute 192.168.1.51
traceroute to 192.168.1.51 (192.168.1.51), 64 hops max, 52 byte packets
 1  192.168.1.51 (192.168.1.51)  27.855 ms  2.296 ms  35.563 ms

Why VNC isn't work when OpenVPN client connected on VNC server and how to bypass this behaviour? I need connect VNC server to OpenVPN network and don't lost VNC connection in same time.

networking vnc openvpn tightvncserver

2 Answers

  1. Option #1

    Try sshing from B to A (in a terminal), and then using it as a tunnel to connect VNC. Steps:

    1. ssh -l <user name> -L 59000:localhost:5900 <server A>. Or ssh -L 59000:localhost:5900 <user name>@<server A> Notes: <user name> is only needed if not the same in the server and client. 59000 and 5900 can be changed. <server A> can be named in ~/.ssh/config or used directly with ip.
    2. VNC to localhost:5900.

    Sources:

    1. https://www.techrepublic.com/article/how-to-connect-to-vnc-using-ssh/
    2. https://health.ucdavis.edu/irc/content/start/computing/vnc_ssh_tunnel.html

    Option #2

    Get the IP of server A in the network and VNC to that IP.

    Related

    1. https://superuser.com/questions/744022/cant-vnc-to-a-machine-connected-through-openvpn
    2. https://forums.untangle.com/openvpn/12376-vnc-through-openvpn.html
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  2. Best Answer

    In my case i just switch ON this switch across OpenVPN Network in Settings -> Sharing -> Screen Sharing on vnc server OS. You need physical access to vnc server machine and connect OpenVPN first.

    Screen Sharing Settings

    Now all works!

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