Map an IP address to the ASN that announces it, with the BGP prefix
Runs in your browser. Only the lookup you start is sent to cloudflare-dns.com or dns.google; nothing else leaves your device. Updated on 25 Oct 2026.IP to ASN mapping tells you which network announces an address. Type an IPv4 or IPv6 address such as 8.8.8.8 for its AS number, BGP prefix, network name and which of the 5 regional registries allocated it. 192.168.1.10 is answered at once, with no lookup: a private address (RFC 1918), used only inside a local network.
Type an IPv4 or IPv6 address, such as 2001:4860::1, in IP address or AS number.
Press Look up to get the AS number that announces the address.
Read the BGP prefix column for the address block that covers the IP.
Read Country as where the block was registered, not where the device is, then press Copy result.
The internet is made of tens of thousands of autonomous systems: networks such as an ISP, a cloud provider or a university, each with its own AS number, that tell each other which address blocks they carry using BGP. This ASN lookup takes an IP address and tells you which of them announces it, or takes an AS number and tells you who it belongs to.
For an IP, the page shows the origin AS, the BGP prefix that covers the address, the country and regional registry (ARIN, RIPE NCC, APNIC, LACNIC or AFRINIC) and the allocation date, then the AS's registered name. When more than one prefix covers the address, the most specific one is listed first, because that is the route traffic follows. When two networks announce the same prefix, the page says so: that can be deliberate, or a sign of a route leak.
Private and reserved addresses, such as 192.168.x.x or 10.x.x.x, are recognised on the page and never sent anywhere: no network announces them. The tool does not give a street location or the person using an address. The country is where the block was registered, which is often not where the device is.
The rest of the article, and all 6 questions about ASN Lookup, are on the ASN Lookup page.
An autonomous system number identifies one network on the internet, such as an ISP, a cloud provider or a large company, that announces its own blocks of addresses to other networks using BGP. Google is AS15169 and Cloudflare is AS13335. Regional registries such as ARIN and RIPE NCC assign the numbers.
Type the IP address. The page asks Team Cymru's routing data which AS announces it, then asks for that AS's registered name. The answer shows the AS number, the organisation, the BGP prefix covering the address, the registry and the country it was allocated in.
Only roughly. The country shown is where the address block was registered, which for a cloud or mobile network is often a different country from the device using it. An ASN lookup names the network, never a street address or the person behind a connection.
No network is announcing it in the global routing table. Private ranges such as 10.0.0.0/8 and 192.168.0.0/16, documentation ranges, and blocks that are allocated but unused all have no origin AS. A block that started being announced only recently may also be missing until Team Cymru's data catches up.
Still stuck? Ask about ASN Lookup and anybody who knows can answer. No account needed.
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On the related tools: Open Port Checker – See if a port forwarded on your router is reachable from the internet.