Re: Maybe I'm misreading this but...

["John A. Tamplin" <jat () traveller com>]

On Fri, 16 Oct 1998, I Am Not An Isp wrote:

> So, as I stated in my last post, it will work unless you filter RFC1918
> space.  I've received lots & lots of replies saying "I filter it", or "I
> RFC1918 in my own LAN, so the firewall drops the packets assuming they are
> spoofed" or stuff like that.  This is fine, and possibly even desirable.
> However, there is nothing to distinguish a packet with RFC1918 space as the
> source address from any other "legal" packet on the 'Net other than your
> own administrative policies - which can break *anything* on the 'Net, not
> just PMTU with RFC1918 space.  Sorry, but I have no control over your
> policy.  So, if someone asks "does this break...", the answer is no.

Well, with this definition, I could just decide to start using someone
else's address space and if you filter it your policies have broken
things, not me. Private address space is intended to be used for networks
not directly connected to the Internet.  We filter every external link to
prevent private addresses flowing in either direction, outside packets
claiming to be from our address space, inside packets not coming from our
address space (and transit customers), and inside packets going to our
address space.  Until router CPU or number of filter entries are a problem,
it makes sense to make sure everything is what is expected, and to drop
anything that isn't.

If they really don't want to use up valid addresses for the point-to-point
links, why not just run the interfaces unnumbered instead?

John Tamplin                                    Traveller Information Services
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