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ASN Lookup
Find who runs an autonomous system, every IP prefix it announces, or the ASN behind any IP address.
About ASN Lookup
An ASN lookup shows the autonomous system behind a network: the number that internet providers, cloud companies and other large networks use to exchange routes with BGP. Enter an AS number to see who holds it, which regional registry assigned it, whether it currently announces routes, and every IPv4 and IPv6 prefix it announces. Enter an IP address instead to find the prefix and ASN that cover it. The data comes from RIPEstat, which combines registry records with live routing tables from the RIPE RIS collectors.
What the results mean
- Holder: the organization name registered for the number.
- Registry: the regional internet registry, or IANA block, the number came from.
- Announced: whether the network currently originates routes seen by the RIPE RIS collectors. Transit-only networks can show no prefixes of their own.
- Prefixes: the IPv4 and IPv6 blocks the network announces, with the total number of IPv4 addresses they cover.
Special AS numbers
| Range | Use |
|---|---|
| 64512 to 65534 | Private use, 16-bit (RFC 6996) |
| 4200000000 to 4294967294 | Private use, 32-bit (RFC 6996) |
| 64496 to 64511, 65536 to 65551 | Documentation (RFC 5398) |
To see where an address is and which provider uses it, try the IP lookup. The WHOIS lookup shows the registration record for an IP range.
Sources: RIPEstat data API, IANA number resources, RFC 6996, RFC 5398.
Frequently asked questions
What is an ASN?
An autonomous system number identifies a network that makes its own routing decisions on the internet, such as an internet provider, a cloud company or a large university. Networks use these numbers in BGP to tell each other which IP prefixes they can deliver traffic to.
How do I find the ASN of an IP address?
Enter the IP address above. The lookup finds the prefix that contains it in live routing data, names the AS that announces that prefix, and shows the network's other prefixes. Our IP lookup also shows the ASN next to location and provider.
What are private AS numbers?
RFC 6996 reserves 64512 to 65534 and 4200000000 to 4294967294 for private use inside a network, the way 192.168.x.x addresses are used at home. They never identify a public network, and the lookup labels them instead of searching for an owner.
Who assigns AS numbers?
IANA hands out blocks of numbers to the five regional internet registries (AFRINIC, APNIC, ARIN, LACNIC and RIPE NCC), and they assign individual numbers to networks in their region. The lookup shows which registry the number came from.