North American Network Operators Group
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Re: Blackhole Routes

  • From: Pete Templin
  • Date: Thu Sep 30 15:44:30 2004

Deepak Jain wrote:

If providers start tying their customer's blackhole announcements to the provider's upstreams' blackhole announcements in an AUTOMATIC process, bad things <tm> are likely to happen. What happens when a customer of a provider mistakenly advertises more routes than he should [lets say specifics in case #1] you can flood your upstreams' routers with specifics and potentially cause flapping or memory overflows...

In case #2, presumably the blackhole community takes precedence, so if a customer is mistakenly readvertising their multihome provider's table with a 666 tag, all of the upstream providers might be blackholing the majority of their non-customer routes.

I build two prefix lists for each customer. One represents the exact match routes that I'm willing to propagate, and the other covers "le 32" more specifics of what I'm willing to allow special treatment on. They can't blackhole anything outside what they would otherwise be allowed to announce (and I use it for several other special cases as well). Customers who are single-homed and otherwise static routed are welcome to use BGP for these special cases; their prefix lists reflect the fact that their space is not to be propagated.

pt