Autonomous System Information Lookup — ASN & BGP Prefix Data

An autonomous system is a collection of IP prefixes under single administrative control, identified by a globally unique ASN. BGP speakers exchange reachability information between ASes — when you lookup AS information, you learn who operates the routing domain announcing addresses seen in your logs.

Registry metadata includes organization name, country, and regional Internet registry delegation — ARIN, RIPE, APNIC, and others. That context accelerates abuse reports and peering inquiries.

This page uses action bgp-route with query parameter — identical to bgp-route-lookup. ASN queries trigger prefix enumeration when the BGP view API succeeds. IP queries focus on mapping one address to parent ASN and org fields.

prefixes array lists CIDR strings; prefixCount reports total IPv4 announcements even when display caps at twenty for readability.

Query by ASN when researching a provider's full footprint — cloud regions, anycast pools, and acquisition networks often aggregate under one number. Query by IP when triaging a single suspicious address from SIEM alerts.

Domain input resolves to current A record IPv4 before ASN mapping — useful for paste-from-URL workflows during phishing investigations.

Each prefix entry is a BGP-announced CIDR block. Large providers may announce hundreds of blocks — twenty samples still confirm AS identity for most operational questions.

Missing prefixes with valid ASN metadata means transient API failure, not proof the AS announces nothing. Retry or cross-check with IRR databases.

Peering coordinators verify partner ASN and approximate prefix holdings before signing agreements. Capacity planners estimate address inventory without requesting internal spreadsheets.

Compare ASN from this tool with traceroute AS paths for consistency when diagnosing asymmetric routing.

Route hijacks occur when an AS announces prefixes it does not own. Establish baseline ownership with this lookup — pair with RPKI validation services for continuous assurance.

Incident responders paste attacker IPs to identify hosting providers for abuse@ contacts. Organization and registry fields populate ticket templates.

Same API and JSON shape. BGP route lookup emphasizes routing engineer SEO; autonomous system information lookup targets AS terminology searches. Choose whichever page title matches your team's vocabulary.

Cross-link asn-lookup and reverse-asn-lookup for org-name-first discovery paths.

Call GET /ip-tools/api/extended?action=bgp-route&query=AS15169. Parse asn, organization, country, registry, prefixes, and prefixCount. Cache registry metadata longer than prefix lists.

Respect rate limits when bulk-processing threat feeds.

Students connect abstract BGP lectures to recognizable AS numbers — public DNS resolvers, major CDNs, university networks. Prefix lists illustrate production CIDR aggregation.