Subject: Re: does gif(4) do RFC 2003 IPv4-in-IPv4 encapsulation?
To: NetBSD Networking Technical Discussion List <tech-net@NetBSD.ORG>
From: William Waites <ww@styx.org>
List: tech-net
Date: 03/04/2002 15:03:30 
On Mon, Mar 04, 2002 at 02:32:09PM -0500, Greg A. Woods wrote:
> 
> Does 'gif' really do encapsulation is according to RFC 2003?
>

Based on the example Cisco configs in the man pages gif(4), 
gre(4) and ipip(4), and experience configuring gif tunnels to
talk to a Cisco, I infer the following:

- since the default tunnel type on a Cisco is GRE and the configuration
  examples are identical in both gre(4) and  ipip(4), the standard
  "IP unnumbered" config can be accomplished with either gre(4) or
  ipip(4)

- confusingly, when making a gif(4) tunnel speak to a Cisco, you
  need to tell it "tunnel mode ipip".

So,

Cisco "ipip" != BSD "ipip"
Cisco "ipip" == BSD "gif"
Cisco "gre" == BSD "gre" == BSD "ipip"

Is this correct?

-w