ASN Lookup
Whose network is this IP address on, and which IP ranges does a company own? Enter an IP address, an AS number or an organisation name. The answer comes from live BGP routing data collected by RIPE; your browser asks RIPE directly, and the query is not sent to us.
The app's ASN Lookup answers the same question from your pocket, for any address or hostname, and Traceroute and MTR label every hop on the path with the network it belongs to, so you can see where your traffic leaves your provider.
What an ASN is
The internet is a network of networks, and each one that makes its own routing decisions has an Autonomous System Number. Internet providers, cloud platforms, universities and large companies each have one or more. Every block of IP addresses on the internet is announced in BGP, the routing protocol between those networks, by the AS that carries its traffic. So the ASN is the most reliable answer to "whose network is this address on".
IP to ASN: what it tells you
Look up an address from your server logs, a firewall alert or an email header and you learn which provider or company routes it: a residential ISP, a mobile carrier, a cloud region, a hosting company, a VPN provider. That is often more useful than WHOIS on the address, because cloud and hosting addresses are registered to the provider while the customer using them changes daily.
Finding the IP ranges a company owns
Search the company's name, pick its AS number and the page lists every IPv4 and IPv6 prefix that AS announces right now. That is the starting point for an attack-surface review or for allow-listing a partner. Two caveats: companies that run on AWS, Azure or Google Cloud have no ranges of their own, their servers sit in the cloud provider's AS; and some organisations hold address space that another network announces for them.
How to look up an ASN on your laptop
Team Cymru runs a free mapping service: whois -h whois.cymru.com " -v 8.8.8.8" returns the AS, prefix, country and registry for an address. Over DNS, dig +short TXT 8.8.8.8.origin.asn.cymru.com does the same with the octets reversed. For an AS number, whois AS13335 asks the regional registry for the holder's record, and the RIPEstat and bgp.tools websites show its live routing.
Where the data comes from
RIPEstat, the public data service of the RIPE NCC, built from BGP routing tables collected by its Routing Information Service around the world. Prefix lists are the routes visible over roughly the last day; prefixes seen by only a handful of collectors are left out.