What Are ASN and BGP, and How to Look Them Up
An ASN (Autonomous System Number) identifies an independent routing domain on the internet, usually corresponding to an ISP or a large organization; BGP is the protocol autonomous systems use to exchange routes.
Looking up an ASN reveals the IP ranges it announces and its upstream / peer / downstream relationships with other ASNs, helping you judge an IP's network ownership and route quality.
FAQ
- How do I find which ASN an IP belongs to?
- Look the IP up on this site; the "ASN" field shows the ASN and its owner, and clicking it reveals the BGP topology.
- What do upstream / peer / downstream mean?
- An upstream is an AS you buy transit from, a downstream is an AS that buys transit from you, and a peer is an AS you exchange traffic with on equal terms.
Want to check a specific IP? Enter it on thehome pageto see its full details: location, IP type, risk score, blocklist status and more.
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