Dear colleagues, In May this year there was a feature request from Job Snijders to have RIPEstat provide transitted prefixes for an ASN. See [0] for more details. Over the summer we worked on this feature. As a result we now have a new data call in the RIPEstat API called RIS Prefixes. This data call reports the prefixes for a given ASN that are seen on the AS paths between the origin and RIS. You can see an example using the RIPE NCC's ASN (AS3333): http://stat.ripe.net/data/ris-prefixes/data.json?resource=AS3333&list_prefixes=true The data call supports the additional parameter of tailoring the output to your needs. See [1] for more details. The data is based on data collected by the RIPE NCC's RIS network (see [2]), and the output therefore reflects the perspective of RIS. Important to interpreting the data correctly is the definition of a transit: for this dataset, a transit is defined as any ASN appearing on the AS path for a route that is not the origin. We understand that the term “transit" can also imply the business relationship between networks, which would provide a list of prefixes that could be referred to as prefixes in the customer cone of a network. At this point in time, the customer cone itself cannot be extracted from the RIS data in a way that is exact and reliable. The RIS Prefixes data call provides a SUPERSET of prefixes considered the customer cone. During the coming months we will further investigate the possibilities of determining customer prefixes with RIS/RIPEstat. Meanwhile, we welcome suggestions from the community for approaches to solve this issue. We look forward to hearing from you, Christian Teuschel & Romeo Zwart RIPE NCC [0] https://www.ripe.net/ripe/mail/archives/mat-wg/2015-May/000588.html [1] https://stat.ripe.net/docs/data_api#RISPrefixes [2] https://www.ripe.net/ris