ASN · AUTONOMOUS SYSTEM · IP RANGES

ASN Lookup

Discover the organization, ISP, country, and advertised IP ranges behind any IP address or ASN.

~/pingie - asn-lookup
ready

Type an IP address or ASN (for example, AS15169).

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ASN lookup: find the network behind any IP or autonomous system number

Every device on the internet connects through a network that is identified by an Autonomous System Number (ASN). When you run an ASN lookup, the tool queries two data sources: ip-api.com resolves the IP or ASN to its registered organization and geolocation, and the RIPE Stat API retrieves the full list of IP prefixes that the autonomous system currently announces via BGP. The result is a structured view of who owns a block of internet routing space and which IP ranges they advertise to the global routing table.

Network engineers, security analysts, and IT professionals use this kind of lookup to trace the origin of traffic, verify IP ownership, and map out how address space is distributed across the internet.

What an autonomous system number actually represents

An ASN is a unique numeric identifier assigned to a collection of IP networks under a single administrative domain. Internet service providers, cloud platforms, universities, and large enterprises each operate one or more autonomous systems. BGP (Border Gateway Protocol) uses these numbers to exchange routing information between networks, so that traffic can travel from one corner of the internet to another.

When a network announces a prefix, it is telling the global routing table: "these IP addresses are reachable through me." The set of announced prefixes is what makes an ASN visible and reachable on the internet. The ASN Lookup tool surfaces both the ASN metadata and its current prefix announcements from RIPE Stat, so you see live BGP routing data rather than a static registry snapshot.

How to use the tool: two supported query types

The tool accepts two kinds of input and resolves both to the same output structure.

  1. Look up by ASN number: Enter the ASN with or without the "AS" prefix. For example, both "AS13335" and "13335" are valid. The tool queries RIPE Stat directly and returns the organization name, ISP, country, and the full list of announced CIDR blocks with a total prefix count.
  2. Find the ASN for an IP address: Enter any IPv4 address. The tool first resolves the IP to its owning ASN through ip-api.com, then fetches the same detailed record from RIPE Stat. This is useful when you have an IP and need to identify the network it belongs to.

What the results tell you

Each result set covers the following fields, pulled from live data sources at query time:

  • ASN and ASN name: The numeric identifier and the registered name of the autonomous system.
  • Organization and ISP: The entity that holds the registration and the service provider associated with it.
  • Country, region, city, and timezone: Geolocation data tied to the ASN registration.
  • Announced prefixes: The full array of CIDR blocks the autonomous system is currently advertising via BGP, sourced from RIPE Stat. Some large networks announce thousands of prefixes; the tool returns all of them.
  • Prefix count: A numeric summary of how many IP ranges the AS is announcing.

Because prefix data comes from RIPE Stat in real time, the list reflects current BGP announcements rather than historical or cached data.

When to run an autonomous system number lookup

This kind of query is useful in several practical situations:

  • Investigating suspicious inbound traffic to determine which network or organization it originates from.
  • Verifying that a cloud provider or CDN is routing your traffic through the expected autonomous system.
  • Mapping the IP space controlled by a specific ISP or organization for network planning or security policy.
  • Cross-referencing an IP address found in server logs with its registered network owner.
  • Checking which CIDR blocks a network announces before adding them to an allowlist or blocklist.
  • Supporting email deliverability investigations alongside tools like the DKIM Checker or DMARC Checker , where knowing the sending network's ASN adds context.

How this tool differs from a plain IP geolocation lookup

A standard IP geolocation tool maps an address to a city or country. An ASN checker goes a layer deeper: it identifies the routing entity that controls that address and shows the full scope of IP space that entity manages. Two IP addresses in the same city can belong to entirely different autonomous systems with different owners, policies, and prefix announcements. The ASN number lookup exposes that routing layer, which geolocation alone does not.

The prefix list is the key differentiator. Knowing that an IP belongs to AS13335 is useful; seeing every CIDR block AS13335 announces is what lets you make policy decisions at a network level.

FAQ

An ASN (Autonomous System Number) is a unique numeric identifier assigned to a network or group of networks operated under a single administrative policy. BGP routers use ASNs to exchange routing information across the internet. Without ASNs, there would be no structured way for networks to advertise which IP ranges they control. Understanding ASNs matters when you need to trace traffic origins, verify routing ownership, or build network-level access policies.

Yes. Enter any IPv4 address into the query field. The tool sends it to ip-api.com, which resolves the address to its registered ASN and geolocation data. It then uses that ASN to query RIPE Stat for the full autonomous system record, including all announced prefixes. The two-step resolution happens automatically; you do not need to know the ASN in advance.

The tool accepts two ASN formats: the numeric-only form (for example, 13335) and the standard prefixed form (AS13335). Both resolve identically. It also accepts IPv4 addresses in standard dotted-decimal notation. The query field does not currently support IPv6 addresses or AS-SET names used in IRR databases.

Prefix data is pulled from the RIPE Stat API at the time of your query. RIPE Stat aggregates BGP routing data from multiple route collectors distributed across the internet. The prefixes returned reflect what the autonomous system is currently announcing to the global routing table. Because the source is live BGP data, the list may differ from static registry records such as WHOIS or IRR entries, which are not always kept in sync with actual routing.

A WHOIS lookup queries regional internet registry databases (ARIN, RIPE, APNIC, and others) for registration records. It returns the entity that registered a resource and contact details, but it does not show live routing state. This ASN search queries RIPE Stat for current BGP announcements, so you see which prefixes are actually being routed right now, not just which ones are registered. A network can hold a registered prefix without actively announcing it; WHOIS would show it, but the prefix list here would not.

An IP geolocation lookup maps an address to a physical location (country, city, coordinates) using databases that correlate IP ranges to geography. An ASN checker identifies the routing entity that controls the address and retrieves its full prefix list from BGP data. Geolocation tells you where an address appears to be; the ASN query tells you who controls the network and which IP ranges that network manages. Both tools use ip-api.com for the initial resolution, but the ASN path continues to RIPE Stat for routing-layer detail that geolocation does not provide.

Yes. Large networks such as major cloud providers or global ISPs can announce thousands of CIDR blocks. The tool returns the complete prefix array from RIPE Stat regardless of size. The prefix_count field in the response gives you the total number at a glance. If you are consuming the API programmatically, plan for large response payloads when querying well-known large autonomous systems.

Yes. The endpoint is GET /api/asn-lookup?query=<IP or ASN> . It returns a JSON object with fields including asn , asn_name , org , isp , country , region , city , timezone , prefixes , and prefix_count . You can integrate this into scripts, monitoring pipelines, or security tooling. For guidance on other available tools across the platform, see the Pingie tools directory .

Queries are resolved in real time against external APIs and are not stored as personally linked records. For full details on what data is retained and how it is handled, see the privacy policy . The tool does not require an account or authentication to run a query.

An ASN can be allocated by a regional internet registry without the holder actively announcing any prefixes via BGP. This happens with stub networks, newly assigned ASNs, or organizations that have paused routing activity. RIPE Stat only returns prefixes that are currently visible in the global BGP routing table. A registered but non-announcing ASN will return organizational metadata but an empty prefix array and a prefix count of zero.

When investigating email delivery problems, the sending server's IP is often the starting point. An autonomous system number lookup on that IP identifies the network controlling it, which helps confirm whether the IP is part of a known mail provider's address space or an unexpected third-party network. Combine this with DNS authentication checks using the DMARC Checker to build a fuller picture of whether the sending infrastructure is correctly configured and authorized.

The ASN lookup tool is available without registration or payment for standard queries through the web interface. API access uses the same endpoint and does not currently require an API key for basic use. If your use case involves high query volumes or automation at scale, review the usage terms on the platform to confirm what applies to your situation.