An Autonomous System Number (ASN) is a unique identifier for a network on the internet. If you want to announce IP addresses via BGP, you need an ASN.
Understanding Autonomous Systems
An Autonomous System (AS) is a collection of IP networks under a single administrative domain with a unified routing policy. Each AS is identified by a unique ASN.
ASNs enable BGP routers to identify and communicate with each other. When you announce IP prefixes, you associate them with your ASN, telling the internet "traffic for these IPs should come to AS12345."
Types of ASNs
There are two types of ASNs based on their format.
16-bit ASNs (0-65535)
The original format, now largely allocated. Easier to remember.
32-bit ASNs (65536-4294967295)
Extended format providing more available numbers. Now the standard for new allocations.
How to Get an ASN
ASNs are allocated by Regional Internet Registries (RIRs) based on your geographic location.
Determine your RIR (RIPE for Europe, ARIN for Americas, APNIC for Asia-Pacific)
Demonstrate technical need (multi-homed network or unique routing policy)
Submit application with network documentation
Pay the allocation and annual maintenance fees
ASN and IP Leasing
To use leased IP addresses independently, you typically need your own ASN. This allows you to announce the leased prefixes via BGP and maintain control over your routing.
If you don't have an ASN, IP Market can route traffic on your behalf using our network infrastructure.