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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Blackhole Routes
On Sat, Oct 02, 2004 at 11:06:31PM +0100, Ian Dickinson wrote: > You'd need an additional community to flag this eg. 65001:666 means to > blackhole, 65001:6666 means to propagate it as well. I can't speak for > others but when we blackhole the destination (as opposed to blackholing > the source or mitigating) we often only do it in the direction from > which the attack is coming*. Why drop globally when you can drop > traffic from a subset of the Internet? Your victim will thank you > if 90% of their customer base can reach them, versus none. Similarly, > if they're multi-homed, they may well rely on you NOT propagating. > Maybe this looks different from the perspective of a global Tier-1. No, 65001:666 (or whatever value is chosen for a well known community, for the sake of argument) means to set the next-hop to something that discards packets, and otherwise propagate the route as normal. If you don't want it to be exported in a specific direction, you add no-export or no-advertise or just don't advertise it to peer X just like you would do with any other route. Don't complicate the protocol unnecessarily based on your specific assumptions of how you might or might not use a feature. There is nothing more or less complicated about this than adding a value to the end of http://www.iana.org/assignments/bgp-well-known-communities and declaring it a standard blackhole community. How you use it, how you export it, and who you accept it from, are provider specific policy decisions. However, based on the knowledge that a blackhole community route is no different than a regular route in its ability to cause unreachability if incorrectly announced, I would tend to suspect that most people would choose to allow this to be propagated globally. -- Richard A Steenbergen <[email protected]> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)
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