Routeviews Prefix to AS mappings Dataset (pfx2as) for IPv4 and IPv6


This dataset contains IPv4/IPv6 Prefix-to-Autonomous System (AS) mappings derived from RouteViews data. Files are created on a daily basis, starting from 2005-05-09 for IPv4 and 2007-01-01 for IPv6. The file format is line-oriented, with one prefix-AS mapping per line. The tab-separated fields are:

  • IP prefix
  • prefix length
  • AS number
More detailed information can be found in the README for this dataset. Files from this dataset can be used by CAIDA's ASFinder and various CoralReef tools (for example in the t2_convert -R option).

Note on Multi-origin ASes (MOASes)

The file format changed slightly beginning with the 2010-10-27 prefix-to-AS file. Previously, ASes were listed in sorted order in MOASes (for example, we said "10_20_30" and never "30_10_20"). Now, we sort the ASes according to their frequency of appearance as an origin AS in the source BGP table. For example, suppose is advertised by the ASes 10, 20, and 30, and suppose 7 RouteViews peers saw AS 10 as the origin AS, 4 saw AS 20 as the origin AS, and 29 saw AS 30 as the origin AS. Then the MOAS recorded in the prefix-to-AS file will be 30_10_20, according to descending frequency of appearance as an origin AS. If there is a tie in frequency, then we sort by lexicographical order. With the new sorting order, users who wish to choose "the best" mapping for simplicity (with full understanding of the caveats) can simply pick the first listed AS.

Acceptable Use Agreement

Please read the terms of the CAIDA Acceptable Use Agreement (AUA) for Publicy Accessible Datasets below:

When referencing this data (as required by the AUA), please use:
Routeviews Prefix to AS mappings Dataset for IPv4 and IPv6
You are required to report your publications using this dataset to CAIDA.

Data Access

Download Routeviews Prefix to AS mappings for IPv4 and IPv6 data.

Related Objects

See to explore related objects to this document in the CAIDA Resource Catalog.
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