ASN Lookup

Enter an Autonomous System Number (ASN) to get detailed information about it.


About ASN Lookup

What does this tool do?

Our ASN Lookup tool retrieves detailed information about Autonomous System Numbers (ASNs), including organization details, announced IP prefixes, and neighboring ASNs. It helps identify network ownership and understand internet routing relationships.

Why is this useful?

ASN lookups are essential for network troubleshooting, security analysis, and understanding internet infrastructure. They help identify network owners, trace routing issues, and investigate suspicious network activity by revealing the organizations behind IP addresses.

Who uses this tool?

  • Network administrators - Troubleshoot routing issues and plan network interconnections
  • Security analysts - Investigate suspicious network activity and trace attack sources
  • IT professionals - Understand network infrastructure and service provider relationships
  • Researchers - Study internet topology and analyze network market dynamics
  • ISP engineers - Plan peering relationships and optimize network performance

How to perform an ASN lookup

  1. Enter an Autonomous System Number (ASN) in the input field
  2. ASNs can be entered with or without the "AS" prefix (e.g., "15169" or "AS15169")
  3. Click "Lookup ASN" to query the routing database
  4. Review the organization information and network details
  5. Explore announced prefixes and neighboring ASNs for deeper insights

Example

Looking up ASN 15169 shows it belongs to Google LLC, revealing their massive network infrastructure with thousands of IP prefixes and connections to major internet providers worldwide.

Understanding your results

ASN (Autonomous System Number)
A unique identifier assigned to a network operator by a Regional Internet Registry (RIR).
Organization
The company or entity that owns and operates the autonomous system.
Announced Status
Whether the ASN is currently active and announcing routes to the global internet.
Announced Prefixes
IP address ranges (in CIDR notation) that this ASN announces to the internet for routing.
ASN Neighbors
Other ASNs that directly peer with this ASN, indicating network interconnection relationships.

Common ASN Types

  • Internet Service Providers (ISPs): Large ASNs with many prefixes serving customers
  • Content Providers: Companies like Google, Facebook with global infrastructure
  • Enterprise Networks: Large corporations with their own ASNs
  • Cloud Providers: AWS, Microsoft Azure, Google Cloud with massive networks

Understanding CIDR notation

  • /24 networks: 256 IP addresses (common for small businesses)
  • /16 networks: 65,536 IP addresses (medium to large organizations)
  • /8 networks: 16+ million IP addresses (major internet infrastructure)
  • Prefix aggregation: Larger organizations may announce summary routes

Important notes

  • ASN data comes from public routing tables and may not reflect private peering
  • Some prefixes may be more specific routes not visible in this summary
  • Network topology is complex - neighbor relationships may be indirect
  • Historical data shows current state, not historical routing announcements

Common use cases

Network Troubleshooting

Identify routing issues by understanding which ASN controls specific IP ranges and their interconnection relationships.

Security Investigation

Trace suspicious network activity back to responsible organizations and understand attack infrastructure patterns.

Peering Analysis

Research potential peering partners and understand the competitive landscape in internet infrastructure.

Market Research

Analyze the size and scope of internet service providers and content delivery networks by examining their IP resources.

Understanding autonomous systems

An Autonomous System is a collection of IP networks and routers under the control of a single organization that presents a common routing policy to the internet. ASNs help organize the global internet into manageable, independently operated network segments.

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