ASN Lookup

Look up any Autonomous System Number, IP address or domain to find the network operator, all announced BGP prefixes, routing peers and abuse contact — live data from RIPEstat, no sign-up needed.

Enter an AS number, IP address, or domain name to retrieve full ASN and routing details.
Enter an ASN, IP or domain to retrieve routing details
Type any AS number (e.g. AS15169), IP address, or domain name above to fetch the full network profile from RIPEstat.
Not stored or logged
Real-time — powered by RIPEstat
No sign-up needed

What This Tool Shows You

This tool accepts any AS number (e.g. AS15169), IP address, or domain name and returns the complete public routing profile for that network in real time. For IP addresses and domains it first resolves the owning ASN, then fetches the full dataset from the RIPEstat Data API: organisation name, country, network type, every announced BGP prefix, estimated total address count, BGP neighbour list with relationship labels, and the registered abuse contact.

BGP Prefix List

Every IPv4 and IPv6 CIDR block the ASN is actively announcing in the global routing table, with a one-click copy.

BGP Neighbours

The full list of autonomous systems the network peers with, labelled as upstream, downstream or settlement-free peer.

Network Type & Country

Classified as Cloud, CDN, ISP, Mobile, University, Government or VPN — with the country the ASN is registered in.

Abuse Contact

The registered email address for reporting malicious traffic, spam or scanning activity from IPs within this network.

Understanding Autonomous Systems and BGP

The internet is not a single network — it is tens of thousands of independently operated networks connected to one another. Each of those networks is called an Autonomous System, and each holds a unique AS Number assigned by one of five Regional Internet Registries: ARIN for North America, RIPE NCC for Europe and the Middle East, APNIC for Asia-Pacific, LACNIC for Latin America, and AFRINIC for Africa. The original 16-bit ASN format allowed values from 1 to 65,535; the 32-bit extension expanded that to over four billion.

BGP (Border Gateway Protocol) is the routing protocol that ties all these autonomous systems together. When a network wants to make its IP address ranges reachable from everywhere, it announces them as prefixes to its BGP neighbours. Those neighbours propagate the announcement further, until every router on the internet knows which AS is responsible for which block of addresses. The prefix list you see in this tool is a snapshot of exactly what a given ASN is currently advertising. To investigate a specific IP within any of those prefixes, use the IP Lookup tool, or resolve it back to a hostname with Reverse DNS.

Practical Uses for ASN Data

Frequently Asked Questions

What is an Autonomous System Number and who assigns them?

An ASN is a unique global identifier assigned to a group of IP address ranges operated by a single organisation under a unified routing policy. ISPs, cloud providers, universities, CDNs and large enterprises all hold their own ASN. The original 16-bit format covered AS1 through AS65535; the current 32-bit format extends that to over four billion values. Assignment is managed by five Regional Internet Registries: ARIN (North America), RIPE NCC (Europe and Middle East), APNIC (Asia-Pacific), LACNIC (Latin America) and AFRINIC (Africa).

Getting an ASN requires justifying a need for it — typically by demonstrating multi-homing (connecting to at least two different upstream providers) or providing transit services to other networks. Organisations that only need IP addresses and a single upstream connection do not need their own ASN; they use their ISP's ASN instead. The process and fees vary by registry and region.

What are IP prefixes and how do I read CIDR notation?

A prefix is a contiguous block of IP addresses in CIDR notation — for example 142.250.0.0/15. The number after the slash (the prefix length) indicates how many leading bits of the address are fixed, with the remaining bits available for individual host addresses. A /24 covers 256 addresses; a /16 covers 65,536; a /8 covers over 16.7 million. When an ASN announces a prefix via BGP, it tells every other network on the internet it is responsible for routing traffic destined for that block.

Viewing an ASN's full prefix list effectively maps which IP ranges belong to that organisation — useful for firewall allowlisting, abuse investigation, and confirming that an IP is genuinely owned by the provider it claims to be. You can copy the entire prefix list from this tool with a single click. To break any individual CIDR block into its exact network range, broadcast address and usable host count, use our Subnet Calculator.

What do upstream, downstream and peer mean in the BGP neighbours list?

These labels describe the commercial or technical relationship between the ASN and each of its BGP neighbours. An upstream (shown as "Upstream") is a transit provider the ASN pays to carry traffic to the broader internet — this network provides full routing tables and reachability to all other networks. Losing an upstream cuts off a portion of the ASN's internet reachability.

A downstream is a customer network that pays the ASN for transit — the ASN provides full routing tables to them. A peer (shown as "Peer") is a settlement-free relationship where two networks of roughly similar size exchange each other's traffic directly, typically at an internet exchange point, without either paying the other. More upstream providers means better routing resilience; more peering relationships means lower transit costs and more direct routing paths.

How do I find the ASN for an IP address or domain name?

Enter the IP address or domain name directly into the search box — no pre-lookup is needed. For an IP address, the tool queries ip-api.com to identify the owning AS number and then fetches the full RIPEstat profile. For a domain name, it first resolves it to an IPv4 address via DNS, then follows the same path. The resolved IP is shown in a notice above the results so you can see exactly which address was used.

You can also type the AS number directly in several formats: AS15169, ASN15169, AS 15169, or just the bare number 15169. All are recognised and normalised automatically. Once the ASN is identified, all prefix, peer and abuse data is fetched live from the RIPEstat Data API with no caching.

What is the difference between an ASN lookup and a WHOIS lookup?

An ASN lookup surfaces network infrastructure data: which IP ranges a network controls, how it connects to the global routing table via BGP, how many peers and upstreams it has, and what type of organisation operates it. This is routing-layer information maintained in the BGP routing tables and the RIPEstat database.

A WHOIS lookup surfaces registration records: domain owner, registrar, nameservers, creation and expiry dates — administrative information maintained by domain registries and regional internet registries. For a complete picture of any domain or IP, combine both: ASN lookup for infrastructure, WHOIS for registration, DNS Lookup for live records, and SSL Checker for certificate validity. Each tool surfaces a different layer of the same network.

What are private and reserved ASN ranges?

Certain ASN ranges are reserved for private use and must never appear in the public BGP routing table, analogous to private IP address ranges like 192.168.x.x. In the 16-bit space, AS64512 through AS65534 are private; AS65535 is reserved. In the 32-bit space, AS4200000000 through AS4294967294 are private. AS0 and AS23456 have special reserved meanings defined by IANA.

If a lookup returns one of these private ASNs, it indicates a private test or internal network rather than a publicly registered autonomous system. You may see private ASNs in BGP configurations for internal routing within an organisation or between a customer and a provider that has not assigned the customer a public ASN. They will not have useful data in RIPEstat since they are not publicly announced.

How does the network type classification work?

The tool classifies each ASN into one of eight categories — Cloud / Hosting, Content Delivery, Broadband / ISP, Mobile Network, Internet Exchange, University / Research, Government, or VPN / Proxy — based on keyword matching against the registered organisation name and description from RIPEstat. It is a useful first signal for quickly understanding what a network does.

This classification is heuristic rather than authoritative. Some organisations operate mixed infrastructure that spans several categories — a telco that also runs a cloud platform, or a CDN that also provides broadband. When the classification matters for a security or operational decision, verify it against the full organisation name and description shown in the results, and follow the RIPEstat link for the authoritative registry record.

What is the estimated IPv4 address count and how is it calculated?

The estimated IPv4 address count is the sum of the address space across all IPv4 prefixes the ASN currently announces in the BGP routing table. For each CIDR prefix, the number of addresses is 2^(32 - prefix_length) — so a /24 contributes 256 addresses, a /22 contributes 1,024, and a /16 contributes 65,536.

This is an estimate of announced address space, not a count of active or in-use addresses. Large networks often announce aggregate blocks that contain unallocated subnets, and some prefixes may be announced for routing purposes without all addresses being in use. The number is most useful for comparing the scale of different networks — a residential ISP with tens of millions of estimated IPs versus a small business with a few hundred tells you immediately about the relative size of the two operations.

Is my query stored or logged?

No. Every lookup runs fresh when you submit the form. The ASN, IP or domain you enter is used only to fetch live results from ip-api.com and the RIPEstat Data API, and is not written to any database, not linked to a user profile, and not shared with third parties. No account is required to use the tool and there is no cached result tied to your query.

Standard web server access logs record the URL of each request — which includes your search query as a URL parameter — for security and uptime monitoring purposes. These logs are periodically rotated and are not used for user tracking, behavioural profiling or advertising. You can look up any publicly registered ASN without creating an account or providing any personal information.