RE: misconfiguring the tunnel source address [mech-v2-04]

["Follen, Stephen" <sfollen@enterasys.com>]

On Fri, 20 Aug 2004, Pekka Savola wrote:
> I just checked 4 different implementations: Linux, BSD, Cisco and
Juniper.
> All of them "allow" the administrator to misconfigure the source
addresses.
> This would seem like a hint that the implementors want to give the 
> power to the administrators, or not bother with additional checks. I'd

> be interested if you know of implementations which check the tunnel
source
> address at configuration time?

The Enterasys implementation also does not check the tunnel source
address at tunnel configuration time, primarily because to do so would
be overly restrictive to the admin in terms of order of configuration;
The admin is allowed the flexibility to configure the tunnel first and
then configure the IPv4 interface if (s)he wants to - but that's just an
implementation detail.

IMHO this sort of stuff is not important enough to go into an RFC. It
seems obvious that if the tunnel source address does not exist on the
device, or if there is no route to the remote v4 destination, or ... the
tunnel won't work.