Re: Packets from net 10 (no, not the lyrics)

[Mohamad Eljazzar <eljazzar () ns utk edu>]

On Tue, 23 Sep 1997 bmanning () ISI EDU wrote:

> > What about providers that use portions of the private address space on
> > their network (up to and including the client's serial interface)?
> >
> > Mohamad
> >
> > On Tue, 23 Sep 1997 bmanning () ISI EDU wrote:
> >
> > > > Should I be filtering all reserved space at my border, or would
> > > > it be reasonable for me to expect the big guys not to take packets
> > > > with clearly inappropriate source addresses?
> > >
> > >   Yes you should. (and with kudos to Andrew)

[ access lists deleted ]

> > >
>
>       The operative phrase here is border. 
>       That means ASN border, i.e. where you BGP
>       peer with others.  At the provider/subscriber
>       interface, within your IGP, using RFC 1918 space
>       is ok.

I agree if BGP is running between the customer and the provider.  However,
if:

        - both the provider *and* the customer are using the same private
          address space

   *and*

        - the provider assigns the p2p link addresses from that same
          address space (according to its own subnetting plan)

the question becomes:  where do you apply the filters?  Is it safe for the
provider to assume, in the first place, that its use of private addresses
should extend to customer networks? 

Mohamad