[1166] in linux-net channel archive
Re: Linux as a Ether->SLIP router?
daemon@ATHENA.MIT.EDU (Stephen D. Williams)
Wed Oct 4 17:25:45 1995
From: sdw@lig.net (Stephen D. Williams)
To: linux@VCLINUX.vic.uh.edu (Linux Mail)
Date: Wed, 4 Oct 1995 10:43:34 -0400 (EDT)
Cc: linux-net@vger.rutgers.edu
In-Reply-To: <Pine.LNX.3.91.950930170346.6252A-100000@VCLinux.vic.uh.edu> from "Linux Mail" at Sep 30, 95 05:06:22 pm
> This seems to be a somewhat popular question, but I have yet to see this
> variation and/or an actual solution.
> I have a local ethernet (3 Linux boxes), I would like to use one of them
> (via a slip connection, to another Linux box) as a router for my local
> net to access
> the Internet. I help to administer the net on the other end (At a local
> College) and can assign the machines on my local net actual IP
> addresses. I have IP-forwarding/Gatewaying compiled into the Kernel of
> both machines (on either end of the SLIP connection). I ran routed and
> added routes on the remote Linux box to my network, but I don't
> think I did it right i.e. it didn't work. Since then I have read several
> FAQ's newsgroups, irc'ed, etc, and have got answers from having to use
> SLIRP-PROXY to using IP-masquerading. I don't see why these strange
> methods should be necessary. This should be a simple router. I saw in
> comp.os.linux.networking something about a gated daemon? but I have
> Gatewaying compiled into the kernel...
I did this for a long time in my house/Internet ISP:
The dialout router machine just needs a default route to the Slip device.
In some situations, you need to set the route to the point-to-point address.
Add a route for the network or individual local machine IP's pointing
to the ethernet device. The other local machines just have a default
route to the local slip machine, and possibly network or individual
routes for other local machines.
The machine at the other end should just have a routes for the network
and/or individual machine addresses at the remote end.
All addresses involved have to be routed to the network that the
remote machine is on. (Ie. you can't just use IP addresses and expect
the 'central' Internet backbone routers to send them to your SP.)
Some OS's still require you to use whole or subnetted class C's for
parts of the above, but it can all be done with individual IP's with
the current Linux kernels and networking commands.
IP Masquerading is used if the local machines have the illegal (ie.
private) IP address ranges and want to use one legal address on
the slip machine to represent all their connections. It's a good
firewall technique, but I haven't tried to do it with Linux yet.
(Waiting for it to become more mature and to get time to experiment.)
> It seems to me I should configure it as a simple ethernet router, and it
> shouldn't matter that one of the interfaces is sl0.
>
> Any help would be greatly appreciated.
> If you need more information please contact me.
>
> linux@vclinux.vic.uh.edu
sdw
--
Stephen D. Williams 25Feb1965 VW,OH (FBI ID) sdw@lig.net http://www.lig.net/sdw
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