What is an ASN?
The internet isn't just a cloud of computers. It's a network of networks. ASNs are the IDs that make this possible.
An Autonomous System Number (ASN) is a unique identifier assigned to every distinct network on the internet that wants to exchange routing information with other networks. If IP addresses are street addresses, ASNs are the postal codes for entire cities or districts.
How BGP Works
The Border Gateway Protocol (BGP) uses ASNs to decide the path traffic should take.
- ISP A (AS12345)
- ISP B (AS67890)
Traffic flows between ASNs based on trust and peering agreements.
Who Needs an ASN?
ISPs
Internet Service Providers like Comcast, AT&T, or Verizon need ASNs to route traffic for their millions of customers.
Content Giants
Companies like Google, Netflix, and Facebook use their own ASNs to optimize content delivery speeds globally.
Frequently Asked Questions
How do I look up an ASN?
You can use an ASN lookup tool or query the WHOIS database. If you know an IP address, you can find which ASN owns it.
Who assigns ASNs?
Regional Internet Registries (RIRs) like ARIN (North America), RIPE (Europe), and APNIC (Asia Pacific) are responsible for assigning ASNs to organizations.