Re: What were we saying about edge filtering?

On donderdag, sep 4, 2003, at 18:51 Europe/Amsterdam, Owen DeLong wrote:

Source address-based filtering in the backbone is expensive and, in many cases, non-feasible.

And, of course, unnecessary. Everything in the core must have gotten there over a border towards some external network or an edge towards a customer (counting own servers and stuff as "customer" too) so if filtering is done there, no need to repeat it in the core. BTW, from what I can tell on a pretty old/slow Cisco box, uRPF makes packet forwarding take about 10% more CPU, which is the same as a short standard access list (which can only look at source addresses). A short extended access list takes around 20% more CPU.