Subject: Re: nat configuration
To: Andrew Brown <firstname.lastname@example.org>
From: Brian Somers <brian@Awfulhak.org>
Date: 01/22/2001 01:36:25
> >> >Hmmm.... I just tried it, and now it works! I thought it didn't used to.
> >> >Either I misremembered, or it's been fixed.
> >> um...what works? a more current nat can mux pings?
> >Yes. My 1.5 NAT box seems to be multiplexing pings. I had one box ping
> >ftp.netbsd.org, and another ping cvs.netbsd.org, and they both worked. My
> >nat config looks like yours, except that I have my hard IP in there
> >instead of 0.0.0.0, and I am using the outgoing ethernet card. :-)
> make it more interesting, just to amuse me? ping the same outside
> address ( i usually use 22.214.171.124) from two machines inside the nat
> and lemme know if it works.
Yes, it works. libalias (used by user-ppp) recognises icmp traffic,
and nat's the sequence number and IP.
> >> >All my machines are running 1.5.
> >> all my machines are running current with less than a two month lag
> >> behind today.
> >I hope it didn't get fixed then broken.
> me too.
It still works (and will continue to).
> >> >If it really works with userland ppp (which I thought was a downgrade from
> >> >1.5's ppp) but not kernel ppp, then there's a ppp bug.
> >> the userspace ppp is, afaik, a *completely* separate and distinct
> >> implementation of ppp. all it requires of the kernel is a serial
> >> interface (with a modem) and a tunnel interface (for packets to go
> >> through). it's not a downgrade...perhaps a "sidegrade".
> >I thought they were based on the same ppp project. The reason for the ppp
> >package was that it's set to version 2.3.11, which is newer than the ppp
> >in 1.4. But 1.5 and current are using ppp 2.4, which is newer, thus an
> >overall downgrade.
> they might have some common roots, if you dig far enough back (like
> netbsd and freebsd), but the userspace one and the kernel space one
> are very different.
user-ppp was originally written by IIJ and was picked up by me and
almost entirely re-written (multi-link support made this necessary)
> some examples: the userspace one doesn't use
> chat...it does it all itself;
Although it can use an external chat program too (see the man page).
> the userspace one does nat all by
> itself, it doesn't rely on the kernel;
Using libalias. libalias does a whole bunch of things, including
non-passive ftp, irc, cuseeme, transparent proxying, pptp, NetBIOS
and realaudio (smedia).
> the userspace one also claims
> to support mppp, which i've not tried,
Yep, works nicely with i4b :-)
> whereas pppd says that only
> works under linux. that might sounds a bit slanted, but those were
> the first things i thought of.
The only downside with user-ppp is the overhead of passing everything
out then back into the kernel. This is being addressed (albeit
slowly) by making user-ppp use netgraph(4) if it's available.
> >> the nat (called aliasing) in the userspace ppp is what actually
> >> handles the multiple outbound pings. i imagine it's fiddling with the
> >> icmp echo request identifier and using it as it uses the local port
> >> number rewriting for udp and tcp.
> >Does it work with that aliasing off?
> not for me, no, since none of my inside machines addresses are routed
> back to me properly. that's something i've been meaning to deal with,
> but haven't yet.
It'll work with ipnat turned off, but not with user-ppp's -nat (or
``nat enable yes'') disabled.
> on a side note, i just thougfht about it a tiny bit more and
> remembered that my nat rules rewrite traffic over ppp0, not tun0,
> which is what the userspace ppp uses. so, no conflict.
They shouldn't get in eachother's way.
I've been intending to make a ppp package for NetBSD, and now see
that there already is one :-) Now that sup.NetBSD.org exports
pkgsrc, I'll look into keeping things more ``available'' :-)
> |-----< "CODE WARRIOR" >-----|
> email@example.com * "ah! i see you have the internet
> firstname.lastname@example.org (Andrew Brown) that goes *ping*!"
> email@example.com * "information is power -- share the wealth."
Brian <brian@Awfulhak.org> <brian@[uk.]FreeBSD.org>
Don't _EVER_ lose your sense of humour !