What Is an ASN?
An ASN (Autonomous System Number) is a unique identifier assigned to a network or group of networks under a single administrative control that connects to the internet. ISPs, large companies, universities, and cloud providers each have their own ASN. For example, Google's ASN is AS15169 and Cloudflare's is AS13335. ASNs are used by Border Gateway Protocol (BGP) to route internet traffic between different networks.
What is an Autonomous System?
An Autonomous System (AS) is a collection of IP address ranges (prefixes) managed by a single organization with a unified routing policy. When you connect to the internet, your traffic passes through multiple autonomous systems to reach its destination. Each AS is identified by its ASN and announces which IP ranges it controls to other networks via BGP.
How to find the ASN for an IP address
Enter an IP address in the lookup tool above and it will return the ASN, the organization name, the country, and the IP ranges associated with that AS. This is useful for identifying which company owns an IP address, investigating suspicious traffic, or understanding network routing.
What is the difference between an ASN and an IP address?
An IP address identifies a specific device or connection on the internet. An ASN identifies the entire network (autonomous system) that owns a range of IP addresses. One ASN can control millions of IP addresses. For example, entering any Google IP address will return AS15169 which controls all of Google's IP ranges globally.
What is BGP?
BGP (Border Gateway Protocol) is the routing protocol that uses ASNs to direct internet traffic between autonomous systems. It is how networks advertise which IP ranges they own and how traffic finds its way across the internet. BGP is often called the glue that holds the internet together.
How do I find my own ASN?
Look up your public IP address using the IP lookup tool on the MyIPNow homepage, then enter that IP into the ASN lookup tool above. It will show you the ASN of your internet service provider and the IP ranges they control.