15% off your first purchase with code WELCOME15, up to 25 GB.

See pricing
ARC Proxies

Glossary · Networking

ASN (autonomous system number)

An ASN (autonomous system number) is the identifier of an autonomous system — a network such as an ISP, a mobile carrier or a cloud provider that announces its own IP prefixes to the internet under one routing policy — so looking up the ASN of an IP address tells you who operates the network it comes from.

Reviewed 30 Oct 2026

See alsoISP proxyDatacenter proxyCarrier-grade NAT (CGNAT)Geo-targeting

How ASNs are assigned

IANA allocates blocks of AS numbers to the five regional internet registries — AFRINIC, APNIC, ARIN, LACNIC and RIPE NCC — which assign them to network operators. RFC 1930 defines an AS as a connected group of IP prefixes run by one or more operators with a single, clearly defined routing policy.

Numbers were originally 16-bit; RFC 6793 extended BGP to carry four-octet AS numbers. Some ranges never appear on the public internet: 64512–65534 and 4200000000–4294967294 are reserved for private use, and 64496–64511 and 65536–65551 for documentation.

Why the ASN tells proxy types apart

Proxy typeTypical network owner behind the exit's ASN
Datacenter proxyHosting or cloud provider
ISP proxyConsumer ISP, though the server is hosted
Residential proxyConsumer ISP, on a subscriber connection
Mobile proxyMobile network operator

The ASN is the cheapest signal a site has: one lookup per address, no behaviour required. It is why the same request can be answered differently from a cloud server and from a household.

Checking an exit's ASN

Query the registry's whois for the exit address, or a routing lookup service that maps prefixes to their origin AS. Do it alongside the location check described in test proxy location.

FAQ

Questions

Something not covered? Write to contact@arcproxies.io.

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

An IP address identifies one endpoint; an ASN identifies the network that announces the block the address belongs to. One ASN typically covers many prefixes and a very large number of addresses.

Can a website block a whole ASN?

It can treat traffic differently by network, and doing so for hosting ASNs is common. Blocking a consumer ISP's or a carrier's ASN would cut off its real customers, which is why those networks are rarely blocked wholesale.

Can I choose the ASN of my exit on ARC?

No. ARC targeting is by pool, country and city. Choosing the pool decides the kind of network — ISP-registered for ARC Basic, residential for ARC Fast and ARC Ultra, carrier for ARC Mobile — but not a specific ASN.

Sources & review

Last reviewed by the ARC Proxies team. Prices are read from the live catalog at build time.

  1. [1]IETF: RFC 1930: Guidelines for creation, selection, and registration of an Autonomous System (AS)
  2. [2]IETF: RFC 6793: BGP Support for Four-Octet Autonomous System (AS) Number Space
  3. [3]IANA: Autonomous System (AS) Numbers registry

In practice

Where asn matters

ProductISPDatacentre-hosted addresses registered to consumer ISPs — our fastest pool and lowest price per GB, for monitors, price feeds and plain HTML at volume.GuideResidential vs datacenter proxiesResidential, ISP, mobile and datacenter proxies compared: where the IPs come from, how sites classify them, speed, cost and when each is the right tool.GuideHow to test a proxy's locationCheck a proxy's exit IP and geolocation with curl, why IP geolocation databases disagree, and how to verify what the target site actually sees.Use caseProxies for cybersecurity and threat intelligenceInvestigate phishing kits, typosquats and malicious infrastructure from an IP that is not your company's, and see the payload the target audience is served.