ASN / BGP Lookup
AS details and prefixes by ASN, IP or domain.
Enter a target
e.g. AS15169, 8.8.8.8 veya example.com — press ⏎ / ⌘⏎
What is ASN / BGP Lookup?
ASN / BGP Lookup takes an AS number, an IP address or a domain and lists the autonomous system's identity, registry, country and the IPv4/IPv6 prefixes it announces.
An autonomous system is a set of IP blocks under a single routing policy. Knowing which AS an address belongs to is how you find out whose network traffic actually comes from — a hosting provider, cloud platform, mobile carrier or corporate network.
The prefix list is directly usable when writing firewall rules, filing an abuse complaint, or scoping the range behind an attack source.
Frequently Asked Questions
8 questionsWhat is an ASN?
An Autonomous System Number identifies a network with its own routing policy (an ISP, cloud provider or large organization). BGP routes between networks using these numbers.
What does origin prefix mean?
The network block your queried IP is announced under in BGP (e.g. 8.8.8.0/24) — the range that carries the IP to the internet.
Where do the prefixes and neighbour ASNs come from?
Identity data (name, country, RIR, allocation date) comes from Team Cymru's DNS service; announced prefixes and neighbour ASNs come from RIPEstat. If a source does not answer, that section stays empty and the page says so — missing data is never rendered as "no prefixes".
Can I query IPv6?
Currently only IPv4 and AS numbers (like AS15169) are supported. Domains are resolved to their IPv4 A record first, then mapped to an ASN.
Where do I find the ASN?
Just enter an IP or a domain — the tool finds the autonomous system for you. To search by organisation name you'd use the RIRs' own search interfaces (RIPE, ARIN).
Why does the prefix list change?
BGP is a live routing system: networks change their announcements during the day, splitting or aggregating blocks. The list is a snapshot of what's announced; looking different hours later is normal.
Can I derive an organisation's full IP list from this?
Announced prefixes are a good start but not complete: large organisations use several ASNs, announce some blocks via another AS, and cloud providers share IPs between customers. Keep that in mind when writing firewall rules.
Is the ASN enough to file an abuse report?
Usually enough to reach the right party — the ASN's holder operates the network. For a direct contact, query the IP in the WHOIS tool and take the abuse address.