Team Cymru IP to ASN Mapping

Choose WHOIS for a single lookup or a bulk list, and DNS for recurring high-volume queries. Bulk input uses begin/end framing with one address or ASN per line; the provider recommends GNU netcat to avoid incomplete buffered output from some nc variants. Verbose results include origin ASN, prefix and registry fields. All interfaces share feeds refreshed every four hours. Multiple origins, more-specific routes and unfiltered leaks can affect a match, while peer inference is not exact. Country codes come from registry records and must not be used as geolocation. Keep bulk runs to a few thousand entries and preserve the response’s routing context.