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ASN Lookup

Find the Autonomous System by IP address or AS number.

TL;DR:

ASN Lookup retrieves the Autonomous System Number for an IP or domain. Shows hosting provider, country, ASN size, prefix. Useful for identifying companies behind IPs, BGP analysis, discovering connected services.

Examples:
AS NumberUnique network identifier
OrganizationAutonomous system owner
CountryAS registration and location
IPv4/v6 PrefixesIP address blocks in this AS

Why teams trust us

BGP
routing data
100K+
ASes in database
<1s
response time
Free
no limits

How it works

1

Enter IP or AS number

2

Look up BGP tables

3

Get AS data and prefixes

What is an ASN?

ASN (Autonomous System Number) is a unique number assigned to ISP networks, CDNs, and large organizations. By ASN you can identify the IP range owner and track traffic routing.

Search by ASN and IP

Enter AS number or IP — get complete information about the autonomous system.

IP Prefixes

List of all IPv4 and IPv6 subnets announced by this autonomous system.

BGP Peers

Upstream providers and peering connections for this AS.

AS Reputation

Abuse indicators: spam, DDoS sources, known malicious hosts.

Who uses this

DevOps

routing diagnostics

Security

attack source analysis

Network engineers

BGP peer analysis

Developers

CDN identification

Common Mistakes

❌
Confusing AS and IPAS is a set of IP ranges. One IP belongs to one AS, but AS can contain millions of IPs.
❌
Not checking ASN with CDNCDN nodes belong to the CDN provider's AS, not yours. Important for routing diagnostics.
❌
Ignoring AS reputationIf your hosting is in an AS with bad reputation, your emails and content may be blocked.
❌
Not checking peersAS peering connections affect connectivity quality with different regions.

Best Practices

✓
Check hosting ASEnsure your hosting AS doesn't have reputation issues.
✓
Use for diagnosticsASN helps understand where the routing problem is during poor connectivity.
✓
Compare competitor ASesChoosing a better hosting AS can improve routing to key regions.
✓
Add to tracerouteKnowing hop ASNs turns traceroute into a provider routing map.

Get more with a free account

ASN lookup history and BGP route change monitoring.

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What is an ASN and How Does Internet Routing Work?

An Autonomous System Number (ASN) is a unique identifier assigned to a network or group of networks managed under a single routing policy. ASNs are used in BGP (Border Gateway Protocol) to exchange routing information between organisations on the internet. Knowing the ASN of an IP address helps identify its owner, hosting provider, geographic region, and network operator — useful for security investigations, traffic analysis, and blocking malicious ranges at the network level.

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Related tools

IP GeolocationPing & PortsTracerouteDNS Lookup

Learn more

Glossary

Frequently Asked Questions

What is an ASN?

ASN (Autonomous System Number) is a unique network identifier on the internet. Each ISP has one or more ASNs.

How to find ASN by IP?

Enter an IP address in the check field — we show the ASN, organization name, country, and IP range.

Why use ASN Lookup?

To identify the provider, analyze network infrastructure, investigate security incidents, and geolocate IPs.

Related guides

Longer-form reading on this topic from the knowledge base.

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