asn.dev

Autonomous system explorer

Look up a network. See how it is actually wired.

asn.dev is an explorer for autonomous systems and the addresses inside them. Search an AS number, an IP, a prefix, a hostname, or an organisation name.

Your connection

IPv4

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IPv6

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Address space

ASN IP Explorer

Every prefix a network originates, shown as structure rather than a flat list: mask distribution, allocation shape, where it lands geographically, and which blocks carry flags worth a second look.

Context

ASN Details

Who runs the network and what it actually does. Registry and RDAP records, PeeringDB profile, classification, reputation, and a plain language summary for networks that have one.

Topology

Peering

Who a network buys transit from, who it peers with, and who sits behind it, derived from BGP routing tables we parse ourselves rather than from a third party's summary.

Investigation

IP Dossier

Everything about a single address, one tab per question: geolocation and the facility its reverse DNS points at, threat intelligence, registration, and how the internet actually routes to it.

Threat

Blocklists and exposure

Around 30 DNS blocklists, Spamhaus DROP, Shodan's view of open ports and known CVEs, and community threat reports from AlienVault OTX and StopForumSpam, each shown with its source and its caveats.

Interconnection

Internet exchanges

Where a network physically turns up to peer, which address it holds on each exchange fabric, and who else is on the same switch, from Packet Clearing House's exchange directory.

Routing security

RPKI, ASPA and IRR

Whether each announcement is RPKI-valid, which ROAs and ASPA records a network has signed, and what it has registered in RADb and the RIR registries, with stale route objects called out.

Filters

AS-sets

The lists upstreams expand to build customer filters, as registered in every IRR, followed recursively to the networks they resolve to. Search a name like AS-CLOUDFLARE.

Directories

Countries and reports

Networks by registration country, the largest networks by size and connectivity, and every RPKI-invalid route in the table, most widely propagated first.

Looking up addresses in bulk?

asn.dev is built for reading, one network or address at a time. For firewall lists, bulk lookups and machine-readable output, use its sibling asn.ipinfo.app. The two share one cache, so blocklist, Shodan and OTX results match on both.

Press / anywhere to jump to the search box.