Subject: Re: ipip and gif (and protocol tunnels in general)
To: None <>
From: Greg A. Woods <>
List: tech-net
Date: 04/18/2000 23:35:04
[ On Wednesday, April 19, 2000 at 11:43:11 (+0900), wrote: ]
> Subject: Re: ipip and gif
> 	- when you configure gif, you'd configure the inner address pair
> 	  with ifconfig(8), and outer address pair with gifconfig(8).
> 	gif allows more flexible configuration.  and i personally think
> 	gif makes more sense, since outer protocol header has almost nothing
> 	to do with inner tunnel configuration.

(Same with GRE, I think.)

As a side note:  I like those terms ("inner" and "outer") much better
than "end-point" and "source/destination", etc.  They make so much more
sense to me and they apply both to a visual representation of a tunnel
as well as to the way the packet headers are "wrapped".  The gif(4)
manual page (esp. paragraph two) is so much easier to understand than
all the verbiage and diagrams in gre(4).

What still confuses me about tunnels in general though is the question
of whether or not the "outer" addresses have to match (exactly) another
interface address (eg. the "outside" ethernet or PPP interface).  It
would seem to me that they do and if this is so then why specify the
local "outer" address as an address number to {gre,gif}config?  Why not
just specify the associated interface name itself instead?  Does it
really matter if it is possible to specify an alias address or not (even
though that's exactly what I did as described in my reply to PR#9920)?

							Greg A. Woods

+1 416 218-0098      VE3TCP      <>      <robohack!woods>
Planix, Inc. <>; Secrets of the Weird <>