IP & Network

ASN & IP Routing Lookup

Find which network announces an IP address — the AS number, its name, the prefix and the registry.

IPv4 or IPv6 address
Output

Result appears here after you select

{ } How to use

  1. Enter an IP address, v4 or v6.
  2. Select Process.
  3. The prefix, AS number and network name come back together.

{ } How it works

ASN & IP Routing Lookup works on the text you provide. Select Process ▸ and it runs entirely in your browser — nothing is uploaded to a server — then shows the result in the Output panel.

Input

  • IPv4 or IPv6 address — paste or type your input in the left panel (use Sample for an example)

Output

TXT text — copy or download it from the Output panel.

{ } Common uses

  • Work out who actually hosts an address that appears in your logs.
  • Check whether two addresses belong to the same provider.
  • Confirm an address is announced from the network you expect and not somewhere else.

{ } Limitations

  • Only addresses announced on the public internet have an AS. Private ranges, loopback and link-local addresses return nothing, which is correct rather than a failure.
  • Routing data lags reality by hours. A prefix that moved this morning may still show its previous origin.
  • The AS is the network announcing the address, which is often a hosting provider rather than whoever is using it.

{ } FAQ

Is my data uploaded to a server?

No. Everything runs locally in your browser — your files never leave your device.

Can I process more than one file at once?

This tool works on one input at a time.

Is this tool free?

Yes — it’s completely free and needs no sign-up.

Does my IP address get sent to a third party?

No, and that is why this tool works the way it does. The routing data is published by Team Cymru as a DNS zone, so the query goes to the same DNS-over-HTTPS resolver every other tool here uses. An HTTP API would have meant handing the address you are investigating to a company with no other role on this site.

Why are two AS numbers shown for one address?

Because two networks are announcing the same prefix. Usually that is deliberate multi-homing; occasionally it is a route leak or a hijack. Either way it is worth seeing rather than hiding, so both are listed.

What is an AS anyway?

An Autonomous System — one network with its own routing policy, identified by a number. Every route on the internet is announced by one, and the AS number is the most reliable way to say which organisation an address belongs to.