ASN Lookup

Capabilities and processing

Enter a public IP address, an AS number such as AS13335, or a domain (looked up through its first address). Our server asks the RIPE NCC routing database (RIPEstat, from RIPE RIS route collectors) for the routed prefix that contains the address and every autonomous system seen originating it, names up to eight of them, and separately asks the regional internet registry (RDAP) who the address block is registered to.

For an AS number, it reports the holder and whether the network is announcing routes. Private, loopback and carrier-grade NAT addresses are explained without being sent.

Example workflow

The sample address 198.51.100.24 is announced by one network from 198.51.100.0/24 and registered to the same organisation. Break it shows a prefix with two origin networks (MOAS), an address nobody announces, an unused AS number and an IPv6 address.

Limits and interpretation

The announcing network and the registered holder can differ, for example when a provider announces a customer's block. Neither identifies an individual customer or an exact location. Several origins are normal for anycast and multi-homed customers but can also be a misconfiguration or a hijack. Sample answers use documentation addresses and AS numbers. Nothing is stored.

Related tools

BGP route lookup · Reverse DNS lookup · Who hosts this website · All tools · Privacy