ASN Lookup

Validate an Autonomous System Number, generate ready-to-run whois and BGP lookup commands, and learn BGP routing concepts — all client-side.

ASN Lookup

Examples

Enter an ASN on the left to generate lookup commands.

BGP and ASN Quick Reference

Autonomous System (AS)
A collection of IP networks and routers under a single organization's control that presents a common routing policy to the internet.
BGP (Border Gateway Protocol)
The inter-domain routing protocol of the internet. BGP exchanges reachability information between autonomous systems using TCP sessions on port 179.
2-byte ASN
Original 16-bit ASN format supporting values 1–65535. Assigned before 2007 when the 4-byte space was introduced (RFC 6793).
4-byte ASN
Extended 32-bit format (65536–4294967295) introduced by RFC 6793 to expand the address pool. Represented in ASPLAIN (plain integer) or ASDOT notation.
Private ASN Range
64512–65534 (2-byte) and 4200000000–4294967294 (4-byte) are reserved for private use, similar to RFC 1918 IP addresses. They must not appear in global BGP tables.
AS Path
A BGP attribute listing all ASNs a route has traversed. Used for loop prevention and policy decisions. Shorter paths are generally preferred.
Route Reflector
A BGP speaker that re-advertises routes learned from iBGP peers to other iBGP peers, simplifying full-mesh iBGP requirements in large networks.
Peering vs. Transit
Peering is a settlement-free exchange of routes between networks of similar size. Transit means paying an upstream provider to carry traffic to the broader internet.
RPKI / Route Origin Validation
Resource Public Key Infrastructure signs IP prefixes to confirm their authorized origin ASN, enabling BGP route origin validation (ROV) to reject hijacked routes.
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Summary

Validate an Autonomous System Number, generate ready-to-run whois and BGP lookup commands, and learn BGP routing concepts — all client-side.

How it works

  1. Enter an ASN in the input field (e.g. AS15169 or just 15169).
  2. The tool validates the format and shows the normalized form.
  3. Click any command card to copy it to your clipboard instantly.
  4. Use the copied commands in your terminal to query public whois and BGP servers.
  5. Browse the BGP concepts reference at the bottom to learn routing fundamentals.

Use cases

  • Quickly generate whois commands for any ASN without memorizing server flags.
  • Investigate which organization owns a suspicious IP range during security research.
  • Generate BGP route-server queries for network troubleshooting.
  • Reference BGP terminology and concepts while studying for networking certifications.
  • Build terminal one-liners for AS-path tracing and prefix analysis.
  • Validate ASN format before entering it into a configuration file or script.
  • Explore public route collector commands for traffic engineering work.
  • Teach BGP concepts with a concrete ASN example and live command output.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu