ASN lookup
Map IP address to provider, AS number, country and IP range.
How this tool works
An autonomous system number (ASN) uniquely identifies a network in global BGP routing. Hetzner is AS24940, Cloudflare AS13335, Deutsche Telekom AS3320, AWS AS16509. This lookup maps any public IPv4 or IPv6 to its ASN, provider name, IP range (CIDR), country and allocation date — via Team Cymru's DNS whois service. Useful for identifying the provider behind an IP, for geo-routing decisions, or to sort log sources by hosting vendor.
Typical use cases
- Group suspicious web log requests by provider
- Separate cloud-vendor traffic (AWS, Hetzner, Azure) from real end users
- Check a hosting migration — has DNS moved to the new ASN already?
- On suspected DDoS, identify the source providers
Frequently asked questions
How does this differ from RIPE/ARIN lookups?
Team Cymru aggregates RIPE, ARIN, APNIC, AFRINIC and LACNIC and exposes everything via DNS lookup — extremely fast. RIPE/ARIN have full holder details which we do not query here.
Does it support IPv6?
Yes — we use origin6.asn.cymru.com with the reverse-expanded IPv6.
Why is there no match for my IP?
Bogon ranges (private RFC1918, reserved, multicast) are not in BGP routing — they have no ASN. Freshly assigned IPs appear only after 24-72h.
Does the tool return full holder data?
No, only ASN name, country and range. For detailed holder data (tech contact, abuse address) use a RIPE/ARIN whois directly.
How current is the data?
Team Cymru updates multiple times per day from the 5 RIRs. Freshness is typically under 24 hours.
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