What does ASN stand for?
An Autonomous System Number identifies an autonomous system: a network or group of networks under common routing administration. An internet provider can operate several ASNs, while a smaller business may use its provider's connection entirely. Having your own AS number is therefore not a requirement for using the internet.
How do I find the ASN for an IP?
- Open the IP lookup for the public target address.
- Enter the displayed AS number in the ASN lookup. Linked numbers prefill the form.
- Press Enter or the button to run the query.
- Compare registration details, observed prefixes and source-availability messages.
The ASN form accepts, for example, AS3320 and 3320. Use the IP lookup for a complete IP address. The network operator associated with an IP is not necessarily the operator of a website reachable at that address.
How do registration and BGP differ?
RDAP describes number registration, including the responsible registry service and published organisation details. BGP exchanges network reachability information. RIPEstat supplies observations from its data sources. A registered name and an observed origin AS answer different questions; announcing a route is not proof of ownership.
What is an announced prefix?
A prefix represents an address range with a shared network mask. 203.0.113.0/24 is an IPv4 documentation example, and 2001:db8::/32 is an IPv6 example. Do not use these reserved networks as live test targets. An AS can announce many networks. A network may also be observed with several origin ASNs; the count alone does not explain why.
How do I read left, right and uncertain neighbours?
RIPEstat uses these labels for positions in observed AS paths. The direction does not reliably identify customers, transit or peering. Uncertain relationships may be affected by a route collector's own connection. A missing observation does not establish that no connection exists.
Why does traceroute show a different path?
Traceroute examines responding IP hops for a particular measurement. An AS path describes routing information at autonomous-system level. One AS can contain many routers, while filtering and load balancing can affect visible hops. Our traceroute starts in Düsseldorf; the ASN lookup queries data sources rather than measuring a packet path towards the network.
What do missing names and shortened lists mean?
A missing name means no matching mapping is available. “Show all” opens entries already loaded: at most 100 left, 100 right and 200 uncertain neighbours, and 256 prefixes per address family. If a source fails, an empty list does not establish that the network is unused. For important decisions, compare additional observation points and the data's time context.