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Re: ssh local port forwarding stopped working

My first guess would be that port(s) 5900 and/or 5902 have been blocked. Next possibility is that for those credentials a remote user/pwd lookup is being done unexpectedly, the lookup needs to timeout because the credentials are invalid. Is the ID really present locally?

On Tue, May 28, 2019, 12:38 PM Gary Dale <gary@xxxxxxxxxxxxxxxxx> wrote:
I'm running Debian/Testing on an AMD64 machine.

I follow what I believe is a fairly conventional way of connecting to
remote machines. Firstly I establish an SSH tunnel using a command like:

   ssh <remote server public IP> -L 5902:<remote workstation local IP>:5900

where the remote server public IP is that of the router (DD-WRT) with
port 22 forwarded to the local IP of a remote Debian/Stable server. The
remote workstation IPs are in the 192.168.1.* range. The SSH connection
works fine.

Then I connect to localhost:5902 using a VNC viewer (tried a few).  I've
been doing this for a decade with no significant problems.

However I haven't been able to do this since at least yesterday
(previous remote login was a week ago. It worked). No matter which
remote machine I try to connect to, I never get to the password prompt.
Instead the connection attempt eventually attempt times out.

I can log onto a KVM virtual machine running on the remote server using
the Virtual Machine Manager GUI. From there I can connect to the other
(real) machines using the Tight VNC viewer.

Since I can connect to the remote workstations from the VM, the problem
cannot be with their service setup. And since the problem isn't resolved
by using a different VNC viewer from my local workstation, the problem
can't be the VNC client. This just leaves the ssh tunnel - specifically
the port forwarding - as the only common element.