[TriLUG] ssh 'through' a firewall

[Mike Johnson]

Douglas Kojetin [djkojeti at unity.ncsu.edu] wrote:
> hi all-
> 
> i ssh to a computer computer behind a firewall that has access to other 
> computers behind the network that i frequently need to ssh to.  what i 
> normally do is
> 
> ssh user at firstcomputer
> ssh user at secondcomputer

Write a simple script that does this:
ssh -L 2222:secondcomputer:22 -f user at firstcomputer sleep 60 && \
	ssh -p 2222 user at localhost

Or just make it an alias, or something.

What it does is set up a port forward to the second computer through
port 2222 on localhost.  So, if you connect to port 2222 on localhost,
the packets will be forwarded to port 22 on second computer.  -f says
'go into the background' so that the prompt comes back to you on your
local system, while executing the sleep on the remote host.  This keeps
port 2222 open on localhost for 60 seconds.  If you do not connect to
that port in that time, the port will go away.  If it doesn't take long
to make the connection, shorten that time.

Oh, and I'm assuming that the username is the same on both hosts.

Mike
-- 
"If life hands you lemons, YOU BLOW THOSE LEMONS TO BITS WITH 
 YOUR LASER CANNONS!" -- Brak

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