🌐 ASN Lookup - Autonomous System Number lookup

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The selected healthy worker peer will originate this network request.
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Examples: 8.8.8.8, 1.1.1.1, github.com, cloudflare.com, AS15169
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Enter an IP address, domain name, or ASN and click "ASN Lookup" to begin...
🔍 Performing ASN lookup...
⚠️ {{ error }}
ASN Lookup: {{ result.target }} → {{ result.resolvedIp || result.target }}
🌐 Autonomous System Information
ASN: {{ result.asn.number }}
Organization: {{ result.asn.organization || 'N/A' }}
Country: {{ result.asn.country || 'N/A' }}
Registry: {{ result.asn.registry || 'N/A' }}
Description: {{ result.asn.description }}
📍 Geographic Information
City: {{ result.geolocation.city }}
Region: {{ result.geolocation.region }}
Country: {{ result.geolocation.country }}
Timezone: {{ result.geolocation.timezone }}
Coordinates: {{ result.geolocation.coordinates }}
📡 Announced Prefixes
{{ prefix }}
⬆️ Upstream Providers
{{ upstream.asn }} {{ upstream.name }}
❌ No ASN information found for {{ result.target }}
This IP address may not be allocated or may be in a private range.
Query Time: {{ result.queryTime }}ms
Data Source: {{ result.dataSource || 'Multiple RIRs' }}
Timestamp: {{ new Date(result.timestamp).toLocaleString() }}
Resolved IP: {{ result.resolvedIp }}
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ℹ️ About ASN Lookup Tool

What ASN Lookup Shows

ASN Lookup identifies the Autonomous System Number associated with an IP address, domain name, or ASN. An autonomous system is a group of one or more IP prefixes operated with a single, clearly defined routing policy. The ASN is the globally unique identifier used when that network exchanges reachability information with the rest of the internet.

This lookup helps answer questions such as "which network originates this IP prefix?", "which provider is behind this traffic?", and "which registry record should I check for routing or abuse contacts?". Results can include the AS number, registered organization, country or region, registry, announced prefixes, and upstream or peer context when that data is available.

Primary references: RFC 1930 describes autonomous system creation and routing policy, RFC 4271 defines BGP-4, IANA's AS Numbers registry tracks AS number allocations, and the NRO RIR overview explains the Regional Internet Registry system.

Network Operations Use Cases

ASN data is useful when you need a routing-level view of an address rather than only a DNS name or geolocation result:

  • Incident response: identify the origin network for suspicious traffic, spam sources, scanning, or abuse reports.
  • Routing troubleshooting: check whether a destination belongs to the expected origin AS before investigating BGP paths, filters, or peering.
  • Provider and CDN analysis: see whether an address is hosted by an ISP, cloud provider, CDN, enterprise network, or transit carrier.
  • Change validation: compare ASN and prefix data before and after migrations, DNS changes, Anycast rollouts, or provider failovers.
  • Compliance and vendor review: document the network operator behind a service endpoint or third-party integration.

Technical Details

ASNs are allocated by IANA to Regional Internet Registries, and the RIRs assign them to network operators according to regional policy. Public routing data then shows which ASN originates an IP prefix through BGP, the inter-domain routing protocol used between autonomous systems.

  • Domain input: the tool first resolves the hostname to an address, then looks up the ASN for that resolved IP.
  • IP input: the result maps the address to an origin ASN, organization, registry, country, and matching prefix when available.
  • ASN input: an input such as AS15169 can return registry and operator details for that autonomous system.
  • BGP context: announced prefixes and upstream providers describe routing visibility, not necessarily legal ownership of every endpoint.
  • Registry context: RIR data may include allocation records, RDAP or WHOIS endpoints, and administrative or technical contact references.

Concrete Examples

  • 8.8.8.8: commonly resolves to Google-operated ASN data, useful for confirming public DNS traffic attribution.
  • 1.1.1.1: commonly resolves to Cloudflare-operated ASN data, useful for CDN and resolver investigations.
  • example.com: resolves DNS first, then reports the ASN for the returned address, so answers can vary by location or DNS response.
  • AS15169: looks up the autonomous system record directly instead of starting from an IP address.

Limitations and Privacy

  • Routing is dynamic: BGP announcements, upstreams, and DNS answers can change over time or differ by vantage point.
  • ASN is not full ownership proof: an origin AS can represent a provider, CDN, transit network, or hosted customer relationship.
  • Geolocation is approximate: registry country and physical server location may not match the user's actual geography.
  • Multi-homing is common: organizations may use multiple ASNs, multiple providers, or Anycast prefixes for resilience.
  • Security note: only query addresses and domains you are authorized to investigate; submitted targets are sent to the server-side lookup service.
  • Privacy note: avoid pasting confidential internal hostnames or sensitive infrastructure details unless you are comfortable sending them for lookup.

API Usage Example:

POST /api/tools/network/asn-lookup
Content-Type: application/json

{
    "target": "8.8.8.8",
    "includeGeolocation": true,
    "includePrefixes": true,
    "includeUpstreams": false
}
Ready