Date: Thu, 9 Jun 2005 09:01:36 +0930 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Jeremie Le Hen <jeremie@le-hen.org> Cc: Marc Olzheim <marcolz@stack.nl>, FreeBSD-net@freebsd.org, Neo-Vortex <root@Neo-Vortex.net> Subject: Re: Problems with gif tunnels Message-ID: <20050608233136.GX64194@wantadilla.lemis.com> In-Reply-To: <20050608104053.GK41050@obiwan.tataz.chchile.org> References: <20050607093717.GA76296@wantadilla.lemis.com> <20050607100958.GU41050@obiwan.tataz.chchile.org> <20050607093717.GA76296@wantadilla.lemis.com> <20050607094848.GB16223@stack.nl> <20050607231218.GD64194@wantadilla.lemis.com> <20050608084946.GI41050@obiwan.tataz.chchile.org> <20050608095703.GM64194@wantadilla.lemis.com> <20050608195837.Q65103@Neo-Vortex.net> <20050608104053.GK41050@obiwan.tataz.chchile.org>
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--DNzU1U2E89wy37K+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wednesday, 8 June 2005 at 12:40:53 +0200, Jeremie Le Hen wrote: >>> It's currently pushing 7:30 pm, and I was going to send out a reply >>> tomorrow. But indeed, it seems that Linux people prefer GRE tunnels, >>> we prefer (with good reason) IP tunnels, and the whole issue was one >>> of documentation. After changing my tunnel from GRE to IP, it worked >>> (and works) like a charm. > > IIRC, > - Linux uses the ipip module to do IP-over-IP tunnel > - FreeBSD uses the gre(4) interface to do GRE tunnels > - GRE is a Cisco product and means ``Generic Routing > Encapsulation''. I don't know what they mean with the term > "Generic" because I have only seen IP encapsulated tunnel so far. > According to the GRE header, I guess GRE is far more powerful > than a simple IP-over-IP encapsulation, and I would be glad if > someone could explain us what are the benefits of this protocol. > I would conclude by saying that indeed Linux users tend to use > GRE tunnels whereas a IP-over-IP tunnel would be enough, because > they used to be trendy. > >> What is the difference between gre and gif tunnels anyway... the man mages >> were not that informative... > > Read above. Usually gre(4) tunnels are used as simple IP-over-IP tunnel, > so a gif(4) would do the same with less overload (due to GRE header size). > GRE seems far more powerful, but I don't know its benefits. My understanding is that GRE is to IP as PPP is to SLIP: it allows multiple protocols to be encapsulated. I've done some tracing with Ethereal, and the only difference is a four-byte header in front of the payload for GRE; in an IP tunnel, it's simply missing. I've written this up in my diary (http://www.lemis.com/grog/diary-jun2005.html#8), along with the traces. Greg -- The virus contained in this message was not detected. Finger grog@FreeBSD.org for PGP public key. See complete headers for address and phone numbers. --DNzU1U2E89wy37K+ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (FreeBSD) iD8DBQFCp3/YIubykFB6QiMRAvJhAJ9ZXgVqwnVxPcT/cpV1Ld5q7BHmVQCgkn/U VXCnZJmSsXNWjpPERF6tlJ0= =TJXq -----END PGP SIGNATURE----- --DNzU1U2E89wy37K+--
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