[kwlug-disc] ssh and port forwarding

Robert P. J. Day rpjday at crashcourse.ca
Mon Dec 15 14:30:33 EST 2008


On Mon, 15 Dec 2008, Rashkae wrote:

> Rashkae wrote:
> > Robert P. J. Day wrote:
> >>   i have the following scenario:
> >>
> >>   host1  <---------->  host2  <--------->  host3
> >>   (ME)
> >>
> >> i want to be able to do the following from host1:
> >>
> >>   1) ssh directly and normally to host2 (trivial)
> >>   2) using host2 as a gateway, ssh from host1 to get to host3
> >>
> >> from the perspective of host1, host2 will be visible (through a
> >> corporate VPN, but still visible).  host3, on the other hand, will be
> >> "hiding" behind host2 on a totally different and internal network, so
> >> i have to use someone else as a gateway -- direct ssh from host1 to
> >> host3 is out of the question.
> >>
> >>   assume the normal stuff: that host1 has an ssh client, and both
> >> host2 and host3 are running an ssh server of some kind (probably
> >> dropbear, actually), and that the ssh server on host2 is set up to do
> >> port forwarding.
> >>
> >>   i've seen two solutions (local and remote forwarding) that involves
> >> doing all the work on host1 but i'd rather not do that -- i'd rather
> >> keep life on host1 simple, and centralize the forwarding configuration
> >> at host2.  so, as i read it, the direct ssh from host1 to host2 will
> >> still work fine, but what do i do at host2?
> >>
> >>   since host2 *will* be running dropbear, as i read, first, on host2,
> >> i'll invoke:
> >>
> >>    # dropbear -a
> >>
> >> so that dropbear is running in port forwarding mode.
> >>
> >>   in addition, on host2, i'll have to run:
> >>
> >>   # dbclient -L 1234:localhost:22 host3
> >>
> >> does that make sense?  so i can ssh from host1 to host2 normally, but
> >> if i want to sh from host1 to host3, i'll invoke:
> >>
> >>   $ ssh host2 1234
> >>
> >> which will get me to host2, which will then forward me on to port 22
> >> on host3.  am i on the right path here?  thanks.
> >>
>
> After typing all of that previous message, I just realized what you are
> trying to do.. (duh moment for the day), and yes, you are absolutely
> correct.  You can just ignore everything I wrote earlier.

  good, i was suddenly really worried.  actually, i tried the above
and it appears to work.  go figure.

rday
--

========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry:
    Have classroom, will lecture.

http://crashcourse.ca                          Waterloo, Ontario, CANADA
========================================================================



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