ASN to IP Range Lookup — BGP IPv4 & IPv6 Prefixes

Autonomous systems announce IP prefixes in BGP declaring reachability to the global internet. Security teams allowlist or blocklist entire provider footprints by aggregating those CIDR blocks in firewalls and WAF rules. Knowing all prefixes for AS15169 differs from allowing one Google DNS IP seen in logs.

Our lookup fetches public announcement data so engineers draft rules from authoritative prefix lists rather than guessing /24 boundaries from single addresses.

Query AS number directly when researching a provider's full footprint — cloud regions, acquisitions, and anycast ranges appear as multiple prefixes under one ASN. Query IPv4 when logs contain only an address — we resolve parent ASN then fetch that ASN's prefix table.

Unknown ASN resolution returns note explaining failure — verify ASN format AS prefix optional.

prefixes array lists up to thirty IPv4 CIDR strings with prefixCount showing total IPv4 announcements even when display truncates. ipv6Prefixes lists up to ten IPv6 entries with ipv6PrefixCount total. totalPrefixes sums both families for capacity planning.

Large hyperscalers announce thousands of blocks — samples confirm ASN identity while counts communicate scale for rule aggregation decisions.

We query BGPView public API for prefix enumeration at lookup time. Successful responses embed live snapshot data. API failures fall back to ASN registry metadata only with explanatory note — organization and country still useful without prefix list.

BGPView reflects public route collectors — rare private announcements or recent withdrawals may lag minutes to hours.

Export sample prefixes into allowlist objects for CDN or cloud provider maintenance windows. Compare prefixCount growth quarter over quarter when providers expand regions — sudden count jumps may explain new egress appearing in logs.

Avoid copying sample lists alone when prefixCount exceeds thirty — fetch full lists from BGP tools or provider published IP ranges for production rules.

BGP route lookup on our platform overlaps prefix fetch for ASN queries with additional IP-only path metadata. ASN to IP range lookup emphasizes prefix list completeness labels ipv6Prefixes separately and targets engineers needing CIDR exports.

Use both interchangeably for ASN research — choose this page when SEO and UI focus on prefix enumeration wording.

Prefix lists show what BGP reports — not cryptographically validated origin authority. Route hijacks announce foreign prefixes until operators withdraw them. Pair prefix research with RPKI validators for production routing security.

Incident response uses prefix lists to identify whether suspicious IP falls inside expected provider allocations versus unexpected announcements.

ASN lookup returns organization name, country, and registry source before prefix fetch. Country reflects registration metadata — prefixes may serve global anycast edges beyond that country.

Organization strings lag acquisitions — verify critical compliance decisions against multiple sources.

Dual-stack providers announce both families. ipv6Prefixes sample supports IPv6 firewall planning alongside IPv4 — growing traffic requires both rule sets updated when providers expand IPv6 anycast.

IPv6-only input to resolve ASN is not supported — enter ASN directly or IPv4 to discover parent AS then review IPv6 prefixes announced by that AS.

Extended API action asn-to-ip-range-lookup accepts query, asn, or ip parameters. Parse prefixes, ipv6Prefixes, prefixCount, and totalPrefixes into CMDB sync jobs.

Cache prefix lists for hours — BGP announcements change slower than individual IP geolocation. Invalidate cache on provider migration events.