Phil Howard <phil@charon.milepost.com> writes:
Route filtering is not the end of the world.
Wow. Times have changed.
You also need to make sure that the ISPs do not filter routes for parts of their own blocks coming in from other peers. If ISP-A did such filtering, then their own customers will find you unreachable, as well as those in ISP-C if ISP-C sends traffic for you into ISP-A.
I know of no ISPs doing such a thing
Sprintlink did at one point. It's a really good idea to do this in general because it mitigates the disconnectivity customers assigned prefixes out of one's address blocks will suffer if and when someone accidentally(?) announces subnet of those blocks. Inbound filters can be adjusted, you know. Unfortunately the people who have inbound filters have never figured out that they should make this a service that they charge for. However, since inbound announcement filtering is a game anyone can play, I recommend people consider the implications of fee-based filter updating and how it can effect their routing whether or not they are the ones doing the inbound filtering. Connectivity = bidirectional bandwidth + bidirectional reachability. Connectivity = value. Sean.