Packets from net 10 (no, not the lyrics)

Tue Sep 23 16:29:00 UTC 1997

On Tue, 23 Sep 1997 bmanning at 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 at 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