What Is an ASN (Autonomous System Number)?

What Is an ASN?

An Autonomous System Number (ASN) is a globally unique numeric identifier assigned to an Autonomous System — a collection of IP networks operated by one organisation with its own independent routing policy. Think of it as a postal code for an entire network rather than for a single device or address.

ASNs are managed by the Internet Assigned Numbers Authority (IANA) and distributed through five Regional Internet Registries (RIRs). Without ASNs, there would be no reliable mechanism for the internet's routing system to identify which organisation controls which block of IP addresses.

What Is an Autonomous System?

An Autonomous System (AS) is a group of IP networks and routers managed by a single administrative entity — most commonly an ISP, a large enterprise, a content delivery network, or a university. What makes it "autonomous" is that it maintains its own internal routing decisions and announces to the outside world which IP ranges it owns.

Examples include an ISP's backbone network, a cloud provider's global data centre infrastructure, or a university campus network. Any organisation that needs to exchange routing information directly with other networks requires its own AS and therefore its own ASN. You can learn more about the organisations behind ASNs in our guide on what an ISP is.

How BGP Uses ASNs

BGP (Border Gateway Protocol) is the routing protocol that interconnects all Autonomous Systems and holds the internet together. Each AS uses BGP to advertise — or "announce" — the IP prefixes it controls to neighbouring ASes. When you load a website, BGP tables are consulted to find the best path through potentially dozens of Autonomous Systems between your device and the destination server.

Every BGP announcement includes the originating ASN and an AS path listing every network the route has traversed. This makes ASNs central to internet routing, traffic engineering, and network forensics.

Who Gets an ASN?

Any organisation that meets its Regional Internet Registry's criteria may apply for an ASN. Common holders include:

• ISPs and telecoms — Must exchange routes with peers and upstream providers.
• Cloud providers — AWS, Google Cloud, and Azure each operate large multi-region ASes.
• CDNs — Cloudflare, Akamai, and Fastly use ASNs for low-latency content delivery.
• Large enterprises — Multinationals with complex, multi-site network requirements.
• Universities — Academic and research networks often have their own ASes.
• Government agencies — National agencies frequently operate independent ASes.

Regional Internet Registries (RIRs)

IANA delegates ASN and IP address allocation to five RIRs, each responsible for a geographic area:

• RIPE NCC — Europe, Middle East (including UAE), and parts of Central Asia.
• ARIN — North America (USA and Canada).
• APNIC — Asia-Pacific region.
• LACNIC — Latin America and the Caribbean.
• AFRINIC — Africa.

Because the UAE falls under RIPE NCC, organisations here apply to RIPE for ASNs and IP address space.

UAE ISP ASNs: e& and Du

The UAE's two main licensed ISPs each have publicly registered ASNs visible in global BGP routing tables:

• e& (Etisalat UAE) — AS5384. One of the largest ASes in the Middle East, carrying residential, business, and international transit traffic.
• Du (EITC) — AS15802. Du's primary AS for consumer broadband, mobile data, and business services across the UAE.

You can confirm which ASN your connection uses right now by visiting the What's My IP tool, which displays your IP address alongside your ASN and ISP name.

Well-Known ASNs

How to Look Up an ASN

Several free tools let you query ASN information using either an IP address or an AS number:

• BGPView (bgpview.io) — Shows announced prefixes, peers, upstreams, and downstreams for any ASN.
• Hurricane Electric BGP Toolkit (bgp.he.net) — Detailed routing data with AS graph visualisations.
• ipapi.is — Returns ASN, ISP name, and geolocation for any IP address via web interface or API.
• RIPE Stat (stat.ripe.net) — Authoritative data directly from RIPE NCC, ideal for Middle East lookups.

What Your ASN Reveals About You

When you visit a website, the server can see your IP address and derive your ASN. This reveals:

• Your ISP or network provider — e.g., "this user is on e& UAE".
• Broad geographic region — usually country level, sometimes city level.
• Connection type — residential, business, hosting provider, or VPN.

Your ASN does not reveal your name, home address, or precise location. For more detail on what your IP exposes, see our guides on whether your IP is safe to share and whether someone can track your IP.

Why ASNs Matter for Security and Privacy

Security teams rely on ASN data to block traffic from networks known for abuse, enforce geo-based access policies, detect VPN and proxy usage, and trace attack origins through BGP AS path data. If you want to change which ASN your traffic appears to originate from, a VPN routes your connection through a different Autonomous System. Learn more in our guide on what a VPN is and our guide on what a proxy server is.