Re: NSPs filter?

["John M. Brown" <jmbrown () ihighway net>]

But keep in mind that there is a difference between IP Header
Source being RFC-1918, and the payload having a query for 
something in RFC-1918 space.

Yes, dropping packets that you have no valid return path for is not
bad.

Dropping queries from your network asking for things in RFC-1918 space
is also good thing (tm)


On Mon, Aug 05, 2002 at 11:06:50AM -0400, Jared Mauch wrote:
> On Sun, Aug 04, 2002 at 09:15:26PM -0700, Stephen Stuart wrote:
> > > IMO, Commercial ISPs should never filter customer packets unless
> > > specifically requested to do so by the customer, or in response to a
> > > security/abuse incident.
> >
> > Let's say the customer operates some big enterprise network, runs
> > their infrastructure in RFC1918 space ("for security," hah), and spews
> > a couple kilobits of DNS query from that RFC1918 space toward the root
> > nameservers. Assume that either pride or ignorance will prevent the
> > customer from ever asking you to filter what you know to be garbage
> > traffic. Does your rule to "never filter customer packets" mean you're
> > going to sit and watch those packets go by?
> >
> > If yes, why?
>
>       Everyone should turn on either the equivalent of
> the Cisco 'ip verify unicast source reachable-via any' on their
> peer/upstream interfaces as well as to internal and bgp customer
> interfaces that may not be able to be checked with a stricter rpf.
>
>       This will drop packets from people that you have no return
> path for in the cef path.  I know other vendors either have or should
> have this feature.  While it will not stem a true DoS based on real
> ip addresses, zombies, whatnot.. it will stop all the rfc1918 headed
> towards the roots or other space that is not in the global routing table.
>
>       if your vendor doesn't have such a knob, i do suggest asking
> them :)
>
>       i've seen a lot of traffic get dropped by using such a
> check on interfaces.  it is not a large amount compared to
> the overall packets but does reduce what you end up transporting
> and customer support queries about why 10.* is sending them packets.
>
>       - jared
>
> -- 
> Jared Mauch  | pgp key available via finger from jared () puck nether net
> clue++;      | http://puck.nether.net/~jared/  My statements are only mine.