ssh tunneling and "channel 2: open failed: administratively prohibited: open failed"
Mike Cohler
mike.cohler at gmail.com
Tue Jan 23 21:20:50 UTC 2007
Jonathan Underwood <jonathan.underwood <at> gmail.com> writes:
> I am trying to connect to machine C via a tunnel to machine B from
> machine A, with machine A being the local machine.
>
> Machine C is behind a firewall, and so direct ssh from A to C isn't possible.
>
> At the command line, once ssh'd into machine B from machine A, I can
> ssh from machine B to machine A.
>
> So, on machine A (local machine) I run in one terminal (Terminal 1):
>
> ssh -R 8888:C:22 username <at> B cat -
>
> which asks me for my password on machine B, which I duly enter.
>
> Then, on machine A, in a second terminal (Terminal 2) I run
>
> ssh -p 8888 localhost
I had a similar problem a few months ago which took me some time to fathom the
solution needed.
I found the following for my case:
1) From machine A do "ssh -L 12345:C:5900 B" (where B and C are your machine
names in question)
in a first terminal window.
This allows an ssh login from A to machine B where the firewall is, but once
connected is set up to forward in this case port 12345 from the originating
machine A to port 5900 on machine C. Once connected to machine B, then login to
machine C on the standard ssh port. Now the tunnel should be set up with the
correct port forwarding that you want - in this case anything going to poert
12345 on machine A will be forwarded through to 5900 on machine C which is the
standard vnc port.
2) Once this is running then start the vnc connection command in a second
terminal session on machine A going to port 12345, and this will then have the
vnc command running and communicating to port 5900 (default) on machine C via
the tunnel.
It did take me quite some time to work this out, but it has worked consistently
ever since.
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