What Is Autonomous System (AS)?

Autonomous System (AS)

An Autonomous System (AS) is a connected group of one or more IP prefixes run by one or more network operators under a single and clearly defined routing policy.

Autonomous System Number (ASN)

An Autonomous System Number (ASN) is a unique two-byte number associated with an AS. The ASN is used an identifier to allow the AS to exchange dynamic routing information with other Autonomous Systems. Exterior routing protocols such as the Border Gateway Protocol (BGP) requires ASNs to exchange information between networks.

aut-num object

An aut-num object is an object in the Whois database used to register ASN assignment details. For the purposes of this document, aut-num object also refers to the ASN registration objects in NIR databases.

Multihomed

A multi-homed AS is one which is connected to more than one other AS. An AS also qualifies as multihomed if it is connected to a public Internet Exchange Point.

Routing policy

The routing policy of an AS is a description of how network prefixes are exchanged between that AS and other Autonomous Systems.

F.A.Q.