ASN Lookup
Look up any Autonomous System Number (ASN) to find the organization, IP address prefixes (IPv4 and IPv6), peer ASNs, upstream providers, and downstream customers. Enter an ASN number such as AS15169 for Google or an IP address like 8.8.8.8 - all data sourced from the public BGPView API. Fast, free, and no signup required.
Look up any Autonomous System Number (ASN) to find the organization that owns it, its IP address prefixes, peer ASNs, and network details. Enter an ASN number or an IP address to get started.
Enter an ASN (with or without AS prefix) or an IPv4 address to find its ASN
Enter an ASN or IP address
Look up organization, IP prefixes, and peer ASNs
Data sourced from BGPView API. All lookups are proxied through our API - no data stored.
Why Use Our ASN Lookup Tool?
Instant ASN Lookup by Number or IP
Look up any Autonomous System Number by entering the ASN directly (AS15169 or 15169) or by entering any IP address. Our tool automatically resolves IPs to their owning ASN, showing you the organization, country, and network details in seconds.
Complete ASN Details & Prefixes
View comprehensive ASN information including organization name, country of registration, total IPv4 and IPv6 prefixes, estimated IP count, and a detailed breakdown of the network infrastructure managed by the ASN.
Peer, Upstream & Downstream ASNs
Explore the BGP peering relationships of any ASN. See which networks are direct peers, which are upstream providers (transit), and which are downstream customers - essential for understanding internet routing and network topology.
External Links & Cross-References
Quickly cross-reference any ASN on industry-standard platforms including BGP.HE.NET, IPinfo.io, RIPEStat, and Cloudflare Radar. One-click links open detailed BGP routing data, IP ownership history, and traffic statistics for each ASN.
Common Use Cases for ASN Lookup
Network Reconnaissance & Discovery
Identify the organization behind any IP address or ASN during network reconnaissance. Map out the networks used by cloud providers, CDNs, hosting companies, and enterprise networks to understand the infrastructure landscape of any service on the internet.
Security Investigations & Threat Intel
During security investigations, look up ASNs associated with malicious IP addresses to identify the hosting provider or ISP. Track attacker infrastructure across multiple ASNs and understand the network relationships between different threat actor resources.
BGP Routing & Peering Analysis
Analyze BGP peering relationships to understand how networks interconnect. Identify transit providers, peering partners, and customer networks for any ASN. Essential for network engineers planning peering arrangements or troubleshooting routing issues.
Email & Network Troubleshooting
When troubleshooting email delivery or network connectivity issues, look up the ASN of problematic IP addresses. Identify whether traffic is coming from a reputable provider, a known spam source, or an unexpected geographic region.
Competitive & Market Research
Research the network infrastructure of competitors and industry players. Understand which cloud providers, CDNs, and hosting companies are being used by major websites and services. Analyze IP resource allocation and network scale.
Education & Network Learning
Learn how the internet routing system works by exploring real ASNs. See how organizations like Google (AS15169), Cloudflare (AS13335), and Amazon (AS16509) manage their global networks. Understand the hierarchy of transit, peering, and customer relationships.
Understanding Autonomous System Numbers (ASNs)
What Is an Autonomous System Number (ASN)?
An Autonomous System Number (ASN) is a unique identifier assigned to a network or group of networks operated by a single organization that presents a common routing policy to the internet. Every organization that connects to the internet and runs BGP (Border Gateway Protocol) needs an ASN. Large organizations like Google (AS15169), Cloudflare (AS13335), andAmazon (AS16509) each have their own ASNs to manage their global network infrastructure. ASNs can be 16-bit (1-64511, 131072-4199999999) or 32-bit (4199999999+) numbers assigned by Regional Internet Registries (RIRs).
How Our ASN Lookup Works
- Enter Your Query: Type an ASN number (e.g., 15169 or AS15169) or any IPv4 address (e.g., 8.8.8.8) into the search field. Click the quick-test buttons to try well-known ASNs from Google, Cloudflare, Amazon, Meta, and Microsoft.
- API Lookup: Your query is sent to the BGPView API, a free and public BGP route database. If you entered an IP address, it first resolves the IP to its owning ASN, then fetches complete ASN details including organization information, IP prefixes (IPv4 and IPv6), and estimated user base.
- Results & Analysis: We display the ASN name, organization, country, prefix counts, and peer data. Three separate panels show peer ASNs, upstream providers (transit networks), and downstream customers, giving you a complete picture of the ASN's position in the internet routing ecosystem.
Understanding BGP Peering Relationships
- Peers: Networks that exchange traffic with each other without payment, typically through Internet Exchange Points (IXPs). Peering benefits both parties by reducing transit costs and improving latency through direct interconnections.
- Upstreams (Transit Providers): Networks that provide paid transit to the rest of the internet. An upstream provider carries traffic that cannot be reached through peering or downstream relationships. Most networks have 1-3 upstream providers for redundancy.
- Downstreams (Customers): Networks that pay this ASN for transit services. A large ASN may have hundreds or thousands of downstream customers, each of which relies on the upstream ASN to reach parts of the internet not covered by their own peering arrangements.
- PeeringDB & Route Servers: Many IXPs use route servers to manage BGP peering. Organizations list their peering policies on PeeringDB, which network engineers use to establish new peering connections.
Privacy, Security & Availability
Our ASN Lookup tool queries the public BGPView API to fetch ASN information. We do not store, log, or process your queries beyond the necessary API request. The tool is 100% free with no signup, no account, and no usage limits. All data comes from publicly available BGP routing tables and Regional Internet Registry (RIR) databases. Note that the API may have rate limits - if you encounter timeouts, wait a moment before trying another lookup.
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Frequently Asked Questions About ASN Lookup
An Autonomous System Number (ASN) is a unique identifier assigned to a network or group of networks operated by a single organization. ASNs are essential for BGP (Border Gateway Protocol) routing on the internet, allowing different networks to exchange traffic. They come in 16-bit (1-64511) and 32-bit formats, assigned by Regional Internet Registries (RIRs).
Simply enter any IPv4 address into our ASN Lookup tool and it will automatically resolve the IP to its owning ASN. You can also use external services like BGP.HE.NET or ipinfo.io, or run the command `whois <ip-address>` in your terminal and look for the "origin" or "aut-num" field.
An ASN lookup reveals the organization name, country of registration, contact information, total IPv4 and IPv6 prefixes announced, estimated IP count, BGP peer relationships (peers, upstreams, downstreams), and the organization's position in the internet routing ecosystem.
ASNs are assigned by the five Regional Internet Registries (RIRs): ARIN (North America), RIPE NCC (Europe), APNIC (Asia Pacific), LACNIC (Latin America), and AFRINIC (Africa). Organizations must demonstrate a need for an ASN and have a unique routing policy to qualify. Public ASNs range from 1 to 64511 (16-bit) and 131072 to 4199999999 (32-bit).
Peers are networks that exchange traffic without payment, typically at Internet Exchange Points (IXPs). Upstreams (transit providers) are networks you pay to reach the rest of the internet. Downstreams (customers) are networks that pay you for transit. Understanding these relationships reveals how traffic flows between networks on the internet.
This tool currently supports IPv4 addresses for ASN resolution. For IPv6, enter the ASN number directly (e.g., AS15169) to view all IP prefixes including both IPv4 and IPv6 ranges announced by that ASN. The results show separate counts for IPv4 and IPv6 prefix announcements.
16-bit ASNs range from 1 to 64511 and were the original format when BGP was designed. 32-bit ASNs (also called 4-byte ASNs) range from 131072 to 4199999999 and were introduced to address the growing number of networks. Older routers may not support 32-bit ASNs. Both are displayed identically in BGP routing tables.
Yes! Our ASN Lookup tool is completely free with no signup, no account, and no usage limits. Data is sourced from the public BGPView API, which aggregates BGP routing information from multiple collectors and RIR databases. We do not store or log your queries.