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Date:      Thu, 18 Jul 1996 18:45:20 -0400 (EDT)
From:      Kenneth Merry <ken@ulc199.residence.gatech.edu>
To:        brandon@tombstone.sunrem.com (Brandon Gillespie)
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: Retake .. Re: IP masquerading over tunel device
Message-ID:  <199607182245.SAA22791@ulc199.residence.gatech.edu>
In-Reply-To: <Pine.BSF.3.91.960718144020.4613A-100000@tombstone.sunrem.com> from Brandon Gillespie at "Jul 18, 96 02:43:43 pm"

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> Ok, so now that the responses seem to have settled, what is the 
> solution?  I saw many different solutions proposed, with some being 
> related?  To reiterate:
> 
> 1: P100 + FreeBSD + Modem
> 1: PowerMAC + MacOS 7.5
> 
> Both have network cards, I want to use the FreeBSD box as a
> router/proxy/gateway/whatever to the PPP device so the mac can access the
> internet through this machine.  My references to Win95 were in regard to a
> friend who has the same setup, but with a Win95 machine instead, and he
> has it working in Linux. 

	I got a similar setup working last month with my -stable box and my
roommate's Linux machine.  2 computer nuts + 1 phone line == problem.  :)
So, since my modem is faster, I would dial in, and we set it up so we could
both telnet, ftp, web surf, etc., at the same time.  (very slowly, but at
least we were both *doing* something as opposed to having one person online
at a time)

Here's how we set it up:

	The two machines were connected via a crossover 10BaseT cable.
(you could do coax, or whatever, but they were networked together)

On the local machine:
 - turn ip forwarding on.  

On the 'client' machine:  (roommate's Linux box)
 - set the default route to my machine (FreeBSD box w/ modem)

On the local machine:
 - run ijppp as the client for slirp
 - dialin to the remote machine

On the remote machine:  (SGI Indigo 2 in this case)
 - run slirp in PPP mode

	After that, everything magically 'worked'.  Slirp did the
translation/masquerading necessary to get both machines up and running and
web surfing.  My FreeBSD machine forwarded my roommate's packets out over
the ppp connection to slirp, which took care of the rest.  We had the 
connection up for 18 hours one time, until someone called.

	The only caveat to this is that you'd have to use slirp on the
remote end to make it work.  Evidently, it won't work with pppd on the
remote end.  (otherwise you wouldn't be asking about this sort of thing, I
suppose.  :) )

	I assume that once some sort of IP masquerading thing goes into
current (based on divert sockets? or perhaps Soren's in-kernel method?) you 
could use that in concert with PPP and probably get it to work just fine.  

	I do have a couple of questions about the way IP masquerading
works, though.  I'll admit I haven't seen the Linux implementation, but I
have (I think) seen it in action on a network here at GaTech.  It appears
that it uses two different hardware (ethernet) addresses for the same IP
address to distinguish between packets going to the different machines.
One will be the real address of the ethernet card, e.g. 00:40:05:bb:11:22,
and the other one will be something like 1:2:3:4:5:6.  

	Does anyone know if that is indeed how it works?  Is that the way 
the FreeBSD implementation will work?  Would the tunnel implementation of
something like that be any different from running it on a local ethernet?
People here use IP masquerading under Linux so they don't have to buy a
second IP address for a second machine, usually.  (Well, that's not the
only reason, there are some more complex, stupid bugs in the Cabletron hubs
at work here..:) )

> I have full control over the dialup system I am connecting to (I run 
> it).  Infact, it is a multiport master off a FreeBSD box.
> 
> I have no problem in upgrading the P100 to -CURRENT, if this is the 
> solution, but once there what do I need to do?

	As I outlined above, upgrading to current isn't the only solution,
if you're willing to run slirp on the remote end.  Slirp does have some
limitations as compared to standard slip or ppp, but overall it's pretty
cool.  I can send along ppp.conf and .slirprc files, and a few directions 
if anyone wants to try it out.  (I got the slirp/ijppp configuration out of 
the -hackers mailing list archive, so if you just want that, it would 
probably be faster to search the archives. :) )


Ken
-- 
Kenneth Merry
ken@ulc199.residence.gatech.edu
Disclaimer:  I don't speak for GTRI, GT, or Elvis.



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