What Is an ASN?

An Autonomous System Number (ASN) identifies a network that controls a group of IP prefixes and exchanges routing information on the internet.

Example

Google Public DNS is commonly associated with AS15169. Large ISPs, cloud providers, and enterprises each operate one or more ASNs.

Why ASNs matter

ASNs help network operators and security teams understand:

• Who owns a block of addresses
• How traffic may enter or leave a network
• Relationships between upstream and downstream providers

IPLocator ASN lookup

Use our ASN tool to look up details by ASN or by public IP address.