ASN Lookup

ASN Lookup - Find Autonomous System Numbers (ASNs), Network Ownership & Routing Details

ASN Lookup Tool - Identify Autonomous System Numbers (ASNs) and Their Network Ownership

The ASN Lookup Tool allows you to instantly find which Autonomous System Number (ASN) an IP address or domain belongs to.

Each ASN represents a network or a collection of IP prefixes managed by a single organization, such as an Internet Service Provider (ISP), data center, or enterprise network, that defines its own routing policy.

With our ASN Lookup, you can uncover detailed information about:

• IP ownership and network operator
• Routing policies and prefixes
• Geographical registration region
• ASN registry (ARIN, RIPE NCC, APNIC, LACNIC, or AFRINIC)

What Is an Autonomous System (AS)?

An Autonomous System (AS) is a connected group of IP networks under one administrative control. It manages its own routing policies for exchanging traffic with other networks through the Border Gateway Protocol (BGP).

Each Autonomous System is assigned a unique number, the Autonomous System Number (ASN), by a Regional Internet Registry (RIR).

In simpler terms, an ASN helps networks communicate efficiently on the Internet by identifying who controls which routes.

How the ASN Lookup Tool Works

Using the tool is simple and fast:

1. Enter an IP address (e.g., 8.8.8.8) or a domain (e.g., google.com).
2. Click “Lookup ASN” to retrieve ASN data.
3. The tool queries WHOIS, BGP, and RIR databases to identify the AS number, organization, registry, and prefixes.
4. Instantly view detailed information about ownership and routing.

Example Output:

• ASN: AS15169
• Organization: Google LLC
• Country: United States
• Registry: ARIN
• Prefixes: 8.8.8.0/24, 8.34.208.0/20, 8.35.192.0/21
• BGP Status: Active

Information You Can Get from ASN Lookup

• ASN (Autonomous System Number): e.g., AS15169
• Organization Name: The entity managing the network
• Country: Registered country of the ASN
• IP Prefixes / Ranges: IPv4 or IPv6 networks managed by the AS
• Registry: Regional Internet Registry (ARIN, RIPE, APNIC, LACNIC, AFRINIC)
• BGP Status: Active or inactive route announcements

Why Use an ASN Lookup Tool?

An ASN lookup is useful for multiple purposes, including:

• Network Diagnostics: Identify which organization manages an IP or domain.
• Routing Insights: Understand how Internet traffic flows between networks.
• Security Analysis: Detect suspicious or malicious ASNs linked to botnets or spam.
• ISP Research: Compare IP allocations and routing behavior between ISPs.
• Compliance & Monitoring: Verify IP ownership and ensure transparent routing practices.

ASN Lookup vs. IP Lookup

While an IP Lookup provides data about a specific IP address, the ASN Lookup reveals broader ownership and routing data, showing which network the IP belongs to and how it connects to the Internet.

Regional Internet Registries (RIRs)

Every ASN and IP address is assigned by one of five Regional Internet Registries (RIRs):

ASN Number Formats

Originally, ASNs were 2-byte (16-bit) identifiers, allowing up to 65,536 ASNs.

To overcome number exhaustion, 4-byte (32-bit) ASNs were introduced, expanding the capacity to over 4 billion ASNs.

Both formats are currently in use and supported by modern routing equipment.

Types of Autonomous Systems

There are three primary types of Autonomous Systems based on connectivity:

• Stub AS: Connected to only one other AS (no transit traffic).
• Multihomed AS: Connected to multiple ASes for redundancy but doesn’t provide transit.
• Transit AS: Provides connections for other ASes, allowing data to pass through.

Understanding these types helps in analyzing BGP routes and network resilience.

Advanced ASN Lookup Insights

Our Advanced ASN Lookup provides enhanced technical visibility:

• IPv4 & IPv6 Prefixes associated with each ASN
• Upstream & Downstream Peers
• BGP Routing Paths & AS Relationships
• WHOIS Data, Admin, and Abuse Contacts
• Abuse Listings or Security Flags (if applicable)

These features make it a valuable tool for network administrators, cybersecurity analysts, and researchers who need to understand global Internet routing and security posture.

ASN Lookup API (for Developers)

Developers can use our ASN Lookup API to integrate IP-to-ASN queries into their systems.

The API supports plain text, JSON, and CSV formats for automation and reporting.

Example:

curl "https://api.example.com/aslookup/?q=8.8.8.8&output=json"

Response:

{

  "asn": "15169",

  "asn_name": "GOOGLE, US",

  "asn_range": "8.8.8.0/24",

  "organization": "Google LLC",

  "registry": "ARIN"

}

API integration is ideal for:

• Network monitoring systems
• Cybersecurity data enrichment
• Automated IP intelligence reporting

(Note: API access limits may apply depending on usage plan.)

Security and Threat Intelligence Use Cases

ASNs play a crucial role in cyber threat analysis. Many known malicious networks or spam sources are identified by their ASN.

Our tool helps:

• Detect ASNs listed on blocklists (Spamhaus, DShield, Firehol, abuse.ch).
• Identify phishing or botnet-related networks.
• Analyze routing anomalies or BGP hijacks.

Knowing which ASN controls an IP can help you “Know your network, know your adversary, and strengthen your defenses.”

Benefits of Having an ASN

Organizations that operate large networks benefit from having their own ASN:

• Enables direct peering and traffic engineering.
• Improves routing flexibility and control.
• Provides a unique global identity on the Internet.
• Facilitates independent BGP configuration and failover planning.

Stay Informed About Your Network

The ASN Lookup Tool gives you an in-depth view of who controls an IP range, how it’s routed, and through which network.

Whether you’re analyzing routes, tracing ownership, or conducting cybersecurity research, this tool offers accurate, registry-backed insights into the Internet’s backbone.

Stay informed, stay secure, and know exactly which ASN powers your connection.