What is an AS number?

The AS number or Autonomous System number represents a unique code issued to Internet-connected network operators and transit companies. This unique code is used in routing tables to decide how Internet traffic should travel between ISPs for specific routes. In mid-2016 there were 54,000 registered AS networks. As of recently ASNs come in public and private variants.

I pay a different company, why is my ASN wrong?

Some ISPs are resellers for larger network operators and may not have their own dedicated AS, instead leasing blocks of IPs from a large network nearby. If the above test results shows an unrecognised company that's probably the reason.

Is my ASN public or private?

If you are reading this page then your ASN is public. Private AS numbers are reserved for networks which do not route Internet traffic, instead routing information for privately-held networks (which may be connected to the Internet via a gateway using a different, public, ASN).

Are AS numbers portable?

Sometimes. If you signed a contract with APNIC or an NIR for your AS number then it is usually portable. However if the ASN was assigned to your ISP then, when you change ISP, you will be changing ASNs.

As an individual, can I get my own AS number?

Usually no. To apply for an ASN you should have a multi-homed network (that is, a network connected to more than 1 peer or upstream provider) or plan to have a multi-homed network in the very near future. There are also sizable membership (or non-membership) fees for new Autonomous Systems upon registration.

Data provided by the awesome ip-api with permission.