What is my ASN?

Your ASN

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More about your connection

What is an ASN?

An ASN (autonomous system number) is the unique number of the network that carries your traffic. The displayed ASN belongs to the network that announces your IP address to the rest of the internet, usually your internet service provider.

What is an autonomous system?

The internet is made of tens of thousands of independent networks: ISPs, cloud providers, universities, content networks and large companies. Each one that sets its own routing policy is an autonomous system (AS), and each is identified by a number such as AS3320 or AS15169.

How ASNs route internet traffic

Autonomous systems exchange routes using the Border Gateway Protocol (BGP). Each network announces the IP ranges it holds, along with the chain of ASNs a route passes through. Routers use this to choose a path for every packet. When you load a website, your data typically crosses several autonomous systems between your ISP and the site’s host.

Who assigns ASNs?

ASNs are handed out by the five regional internet registries (RIPE NCC, ARIN, APNIC, LACNIC and AFRINIC). Originally ASNs were 16-bit numbers, allowing about 65,000 of them. Since 2007, 32-bit ASNs have been available, which allows over four billion.

Why your ASN is useful

  • Troubleshooting: network engineers use the ASN to identify where traffic is coming from and which provider to contact.
  • Security: firewalls and anti-fraud systems block or score traffic by ASN, for example to flag logins from data centers.
  • Checking a VPN: while a VPN is active, the ASN should belong to the VPN’s hosting provider rather than your ISP.
  • Research: public tools such as bgp.he.net and RIPEstat show an ASN’s IP ranges, peers and routing history.

Frequently asked questions

Do I have my own ASN?

Almost certainly not. The ASN shown belongs to your ISP or the network you are connected through. Only organizations that manage their own routing, such as ISPs, hosting companies and large enterprises, register ASNs.

What is the difference between an ASN and an IP address?

An IP address identifies a single connection. An ASN identifies a whole network that can hold millions of IP addresses and makes its own routing decisions.

How do I get an ASN?

Apply to your regional internet registry, such as RIPE NCC in Europe or ARIN in North America, or through one of their members. You usually need to show that you will connect to at least two other networks.