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BCP38 - Internet Death Penalty

On Thu, Mar 28, 2013 at 1:58 PM, Leo Bicknell <bicknell at ufp.org> wrote:
> But the real power here comes by applying this filter further up the
> food chain.  Consider peering with a regional entity at an IX.  Most
> [...]
> That doesn't turn into a useful packet filter for the peer, but using my
> method the peer could be RPF filtered based on what they send,
> automatically.

Hi Leo,

Be nice if that were correct. If the best route you pick for the
customer's advertisement goes to your upstream instead of your
customer, you won't advertise it to your peer. And if your customer
sets a BGP community defined to mean "don't advertise to peers" then
you won't advertise it to the peer. Yet they may well transmit packets
to you for which delivery to that peer is directed by your routing

Which means that your peer can't take the received routes from your
BGP session as gospel for what source addresses to expect.

Bill Herrin

William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004