I have set up an OpenSSH Server on my PC (running Ubuntu 22.04) to connect to it with my Laptop (running Ubuntu 20.04). Both devices have the NordVPN meshnet enabled and allow all the connection types from other devices in my meshnet (Routing, Incoming Traffic, Local Network Access, Sending Files). I have added the SSH public key from my Laptop to the authorized_keys file on my PC.
Connecting to the server worked from the PC itself (via localhost). It also worked from the Laptop using the meshnet IP, when I was in the same network as my PC.
Now I try to connect from my Laptop from a different network and I only get timeouts:
sudo ufw allow ssh on both devicesservice ssh status on the PC it shows "fatal: Timeout before authentication for <Laptop meshnet IP> port 47176" (this port changes each time)It seems communication is possible (bec. ping works), but something is blocking the authentication. Is there something I need to do on the client device (Laptop) to allow the authentication? Why did it work while in the same network, but not in another?
I appreciate any help.
Update: After trying some different devices and reinstalling nordvpn, I noticed, that the ssh connection works at first, but when I try to use sshfs, the authentication fails and afterwards ssh doesn't work as well.
I'm from NordSec, I verified situation you described - I have 2 computers with Ubuntu 22 VM on each - 4 peers in total. Each VM has OpenSSH service. I am able to ssh-connect into each ubuntu's ssh server from every other peer. I simulated network change (roaming) on one computer and then again was able to ssh-connect. Also, I tried with ssh key uploaded to server and without that i.e. using username+password login.
In your case, it seems to me some temporary problem maybe with stalled linux service (sshd) or FW extra restrictions or some network customization.
Need some additional info about your environment to be able to help you.
UFW is by default not active on Ubuntu, have you activated it and maybe made some customizations/ extra restrictions? Would need to see list for FW rules exported with command sudo iptables-save, also your routing setup information would help to identify the problem (could you show output of ip rule and ip route).
But all this could be quite sensitive and your private information to publish it here publicly. So, I recommend to ask NordVPN support help via support.nordvpn.com page's chat bot just ask for human help. There you will be provided with recommendations how to solve the problem, or what extra information to provide to be able to help you solve that problem.
While this is not exact solution to your problem, but was trying at least to provide the path to the solution.