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ASN prefixes

List every IPv4 and IPv6 prefix a network announces, with a merged list you can paste into a firewall or allowlist.

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How it works

Every network on the internet has an AS number and tells other networks which address blocks (prefixes) it carries. This tool reads that list from RIPEstat, which collects routing data from hundreds of networks around the world. Prefixes that very few of them see are left out.

The merged list is the fewest CIDR blocks that cover exactly the same addresses. Networks often announce a big block and smaller pieces of it, or neighbouring blocks, so merging can shorten the list a lot. Use it for firewall rules or allowlists. The CIDR aggregator does the same for any list you paste.

Routes change all the time, so treat the list as a snapshot. Don't know the AS number? Find it from any IP address with IP to ASN.