From owner-freebsd-net@FreeBSD.ORG  Wed Jun  8 10:41:09 2005
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Date: Wed, 8 Jun 2005 12:40:53 +0200
From: Jeremie Le Hen <jeremie@le-hen.org>
To: Neo-Vortex <root@Neo-Vortex.net>
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Cc: Greg 'groggy' Lehey <grog@freebsd.org>, Marc Olzheim <marcolz@stack.nl>,
	Jeremie Le Hen <jeremie@le-hen.org>, FreeBSD-net@freebsd.org
Subject: Re: Problems with gif tunnels
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> > 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.

Regards,
-- 
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >