Blackholing FAQ
A Blackhole is a prefix for which all destination traffic will be discarded.
The amount of Blackholes is included in the maximum number of allowed prefixes.
This means: (standard prefixes + Blackholes) < maxpref.
The Blackhole can be as specific as /32 (IPv4) or /128 (IPv6).
Many peers do not accept IPv4 prefixes more specific than /24 and IPv6 prefixes more specific than /48. Please ask your peers to accept more specific prefixes.
Please check if your Blackhole announcement is accepted by the route servers. You can check this in the DE-CIX Looking Glass. By entering the blackhole prefix into the global search field, you can get an overview of the networks announcing this blackhole prefix, as well as the route servers and therewith the exchanges where the prefix is visible at.
No. The route servers honor these communities and will not pass on your announcements at all. The route servers will automatically add NO-EXPORT to all Blackholes before exporting them to other peers.
No. This would have the same effect as NO-EXPORT/NO-ADVERTISE as you instruct the route servers to not advertise your prefix(es) to any peers.
Yes, standard DE-CIX route server BGP control communities apply to Blackholes as well. You can e.g. signal a Blackhole to all route server peers except AS64501 by setting the following communities:
- (6695:6695) where 6695 is the AS of the DE-CIX route servers in Frankfurt. Replace this to the corresponding route server AS of each DE-CIX IX
- (0:64501)
For more information about route server BGP control communities, please have a look at our route server guides.
You can check this in the DE-CIX Looking Glass. By entering the blackhole prefix into the global search field, you can get an overview of the networks announcing this blackhole prefix, as well as the route servers and therewith the exchanges where the prefix is visible at.
No, Blackholing is free of charge for customers who use the GlobePEER service.
Blackholing is available at all DE-CIX exchanges, except Berlin, Moscow, and the Internet Exchanges in India.
The Blackholing route server (rsbh) is available at DE-CIX Frankfurt and in Dubai. Have a look at our FAQ for the Blackholing route server.
