ASN Lookup
Look up an Autonomous System Number (ASN), IP address, or domain name to inspect routing registries, assigned prefixes, and managing ISP records.
What is an Autonomous System Number (ASN)?
An Autonomous System Number (ASN) is a globally unique number identifier assigned by internet registries to a group of one or more IP prefix networks managed by a single network operator (such as an ISP, a large university, or a technology corporation). These systems form the structural core of the internet's routing infrastructure, using Border Gateway Protocol (BGP) to coordinate connection pathways and transfer data packets across global points.
Why Conduct an ASN Lookup?
Network engineering teams, security investigators, and threat analysts execute ASN lookups to track the ownership of IP blocks, isolate security breaches to specific host organizations, analyze BGP route optimization options, and prevent malicious server pools from accessing secure services. Mapping IP spaces back to their owning entities is vital for server audits, connection routing maps, and policy compliance tests.
Frequently Asked Questions
What is an ASN?
An Autonomous System Number is a unique identifier assigned to large networks or internet service providers by global registries. It enables routers to manage data routing between different networks using Border Gateway Protocol (BGP).
What does an ASN lookup show?
An ASN lookup displays information about the network owning an IP address. This details the network operator, registry registration dates, physical headquarters country, abuse reporting emails, and the block of IP addresses they manage.
What is BGP routing?
Border Gateway Protocol is the standard postal system of the internet. It dynamically determines the most efficient routing paths for data packets to travel across different networks and autonomous systems to reach their final destination.
Who assigns ASN numbers?
ASNs are distributed by IANA to five Regional Internet Registries (RIRs) worldwide: ARIN, RIPE, APNIC, LACNIC, and AFRINIC. These regional organizations then assign numbers to local ISPs, universities, and businesses.
What is the difference between a 16-bit and 32-bit ASN?
Originally, ASNs were 16-bit numbers, allowing for up to 65,536 networks. As the internet grew rapidly, registries introduced 32-bit numbers, expanding the pool to over 4 billion unique network codes to prevent system exhaustion.
Can I lookup ASN info for a domain name?
Yes, this ASN lookup tool automatically resolves domain names to their active IP addresses first. It then queries the network registration database to find the exact autonomous system number managing that hosting server.