Donate
Donate
BETA

ASN Lookup

Find the ASN and organization for an IP address

How ASN lookup works

ASNs identify network operators. An ASN lookup maps an IP to its announced ASN and organization, typically based on CIDR ranges in routing tables.

Related topics

When ASN lookup is most useful

ASN data is especially helpful for understanding who routes traffic for a given IP. It is not a precise ownership record, but it shows the network announcing the IP range in global routing tables. This is why ASN lookup is a common first step in abuse investigations, troubleshooting connectivity, or validating an ISP.

Results can vary based on how IP ranges are delegated. Large organizations may announce multiple CIDR blocks, while hosting providers may reassign ranges to customers. In those cases, pairing ASN data with WHOIS/RDAP gives you both routing and registration context.

  • Network troubleshooting: see which ASN announces the range and compare it with expected routing paths.
  • Security checks: identify if suspicious traffic is coming from a known provider or a residential ISP.
  • Infrastructure planning: confirm the ASN before setting up peering or firewall rules.

If you want to validate ownership details beyond ASN, use WHOIS/RDAP for registrant information and DNS tools to confirm hostnames and services.

Related Articles

What Is an ASN? (Autonomous System Number) Explained8 min read • January 9, 2026CGNAT IP Address Range (100.64.0.0/10) + How to Check Yours7 min read • January 17, 2026Reserved IP Address Blocks Explained8 min read • January 9, 2026

Frequently asked questions

What is an ASN?
ASN stands for Autonomous System Number. It identifies a network operator and is used by BGP to route traffic between networks.
Why does an IP lookup show ASN?
ASN indicates the network that announces the IP range. It helps identify the ISP or organization behind an IP.
Can one ASN contain many IP ranges?
Yes. Large networks announce multiple CIDR ranges under the same ASN.