[Techtalk] adsl and dyndns issues with changing IP addresses

Conor Daly conor.daly-linuxchix at cod.homelinux.org
Wed Nov 24 23:27:35 UTC 2010

On Wed, Nov 24, 2010 at 09:31:57AM +0100 or so it is rumoured hereabouts, 
Wim De Smet thought:
> Quick recipe:
> ssh -N -L localhost:5000:localhost:5000 <yourremotehost>
> What this does is, if you connect with a client on localhost and port
> 5000 (the first 2 values) on the machine where you run ssh on, it will
> tunnel the connection over to <yourremotehost> and connect to port
> 5000 on localhost there (the second two). This happens to connect to
> localhost, but you could make it www.google.com:80 if you'd so wish.
> You can add -f to background this ssh process (just keyb interrupt it
> otherwise).
> Using ssh-agent or the like you can make sure you don't have to fill
> in password prompts of course. It's perhaps not super robust. For one,
> I'm not sure what will happen when your IP address changes, probably
> the tunnel will take a while to time out and you'd have to use upstart
> or the like to keep an eye out for ssh dying. But it does the trick
> for me when I need to do some testing from home and need to get at the
> DB server.

I extended this idea by having a procmail rule run a script when I sent
the correct email from home.  The script would set up the tunnel _from_
the work server _to_ my home machine so there was never a port open in the
firewall for incoming connections.  I would then connect back by
connecting to localhost:5000

Conor Daly <conor.daly at cod.homelinux.org>
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