About autonomous systems
An autonomous system is a network with one routing policy: a provider, a large company, a university, a cloud. Each has a number from a regional registry. Networks exchange routes with BGP, and every route carries the AS numbers it passed through.
Numbers 64512 to 65534 and 4200000000 to 4294967294 are private (RFC 6996), like private IP addresses, and never appear on the public internet.
Announced prefixes
The prefix counts come from RIPEstat, counting routes seen by at least ten of RIPE's route collector peers, which filters out short-lived and very local announcements.
Questions
- What is a 32-bit ASN?
- Numbers above 65535. The original 16-bit range ran short, so RFC 6793 extended it.