An Autonomous System Number is a distinctive, internationally recognized identification that enables an autonomous system to communicate routing data with other systems. A collection of IP prefixes with a well-defined external routing strategy is known as an Autonomous System (AS).

An ASN is a number that businesses or other parties must obtain from Internet domain registrars in order to set up internal network systems that communicate with other networks via the Internet.

The Internet Assigned Numbers Authority (IANA) has autonomous systems ranging from 1 to 64511 accessible for users worldwide

The 64512 through 65535 series is designated for exclusive and private use. To control networking organizations like Internet Service Providers, academic institutions, and governmental organizations, autonomous systems were first proposed.

Each autonomous system must have a distinct identification for them to communicate with one another. There are both public and private autonomous system numbers. Systems wishing to communicate information through the Internet must use public ASNs. If a system is only using the Border Gateway Protocol (BGP) to communicate with one provider, a private ASN can be deployed in its place.

The Border Gateway Protocol (BGP) is the system that controls prefix advertising, routed peerings, and packet routing between various autonomous systems on the Internet. Each system is uniquely identified by the ASN in BGP. BGP serves as the Internet AS routes’ routing mechanism in practice

Autonomous systems are becoming increasingly important as internet-connected devices and IP addresses grow and spread. To handle the numbers, the IANA and associated groups have transitioned from the IPv4 system to the new IPv6, where additional numerical capacity can aid in managing demand growth.

However, the shift from IPv4 to IPv6 is not yet final, and it remains to be seen how well the present structure will handle increased demand in the future.

What Is an ASN?