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BGP Prefix Lookup

Find which BGP prefix announces any public IP, and which AS originates it.

How to read the result

Routers forward packets using longest-prefix-match: the most specific covering prefix wins. An IP like 8.8.8.8 falls inside the announced prefix 8.8.8.0/24 — this tool shows that covering prefix and its origin AS.

Example

8.8.8.8 → 8.8.8.0/24 originated by AS15169

FAQ

What is longest-prefix-match?

When several prefixes cover an IP, routers use the longest (most specific) one. A /24 beats a /16 for the same address.

Prefix vs ASN?

The prefix is the address block announced on BGP; the ASN is the network operator announcing it.

Why no result?

Private/reserved IPs are never announced on public BGP, so there is no covering prefix for them.