How to get your own ASN
You request an ASN from your regional registry when you run a multi-homed network, meaning you connect to more than one provider and want to control your own routing. You usually need to show a routing policy distinct from your providers. A single-homed network does not need its own ASN.
How to check who an ASN belongs to
To see which organization holds a given ASN, or the ASN behind an IP, use the ASN Lookup tool. For programmatic checks, Abstract's IP Intelligence API returns the ASN and its operator for any IP. To resolve an address to its ASN, see IP-to-ASN mapping.
Frequently Asked Questions
Who assigns ASNs?
IANA allocates blocks of ASNs to the five regional internet registries (ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC), which assign individual ASNs to network operators.
How do I get my own ASN?
Request one from your regional internet registry, usually when you run a multi-homed network with its own routing policy. Many operators get one through an upstream provider.
What are the ASN ranges?
ASNs run from 0 to 65,535 (2-byte) and 0 to 4,294,967,295 (4-byte). Ranges 64512 to 65534 and 4200000000 to 4294967294 are reserved for private use.
What are the five RIRs?
ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC, covering North America, Europe and the Middle East, Asia-Pacific, Latin America, and Africa respectively.
Do I need an ASN for a single network connection?
No. A single-homed network uses its provider's routing and ASN. You only need your own ASN when you are multi-homed and manage your own routes.
