IP to ASN Mapping Service

Simultaneously search thousands of IPs in minutes and gain accurate WHOIS lookup results

How is each service used?

To use the command-line arguments on a single IP query, be sure to enclose the request in quotes and to have a space before the first argument so that your whois client will not try to interpret the flags locally.

For example, to enable the verbose mode (all flags) one would use:

You may also query for some basic AS information directly:

We recommend the use GNU’s version of netcat, not nc. (nc has been known to cause buffering problems with our server and will not always return the full output for larger IP lists). GNU netcat can be downloaded from https://sourceforge.net/projects/netcat/. This is the same as gnetcat in FreeBSD ports.

To issue bulk queries, follow these steps:

1. Create a file with a list of IPs or ASNs, one per line. Add the word begin at the top of the file and the word end at the bottom.​

Example of list01:

Remember: you can add comments and other flags per the table above if you’d like.

2. Run the list through GNU netcat (NOT the venerable nc).

The file list02 will be sorted by origin AS, and should appear as:

3. The same can be done with a list of ASNs

Example of list02:

And the output:

4. Bulk queries can contain IPs AND ASNs, however the output may not be ideal:

Example of list03:

Output:

Additional help can be obtained by issuing the help command:

For additional support or to report an issue, please contact support@cymru.com.

DNS

The same query could be expressed as:

IPv6 queries are formed by reversing the nibbles of the address, and placing dots between each nibble, just like an IPv6 reverse DNS lookup, except against origin6.asn.cymru.com instead of ip6.arpa. Note that you must pad out all omitted zeroes in the IPv6 address, so this can get quite long! For example, to look up 2001:4860:b002::68, you would issue the following query:

You can considerably shorten your query if you assume that the long runs of zeroes are in the host portion of the address (as is often the case with IPv6 addresses:

To query for a given IP/prefix peer ASNs, one would use the peer.asn.cymru.com zone as follows:

When there are multiple Origin ASNs or Peer ASNs, they will all be included in the same TXT record such as in the example above.

Notice that the format is very similar to the data returned in the verbose whois based query. The major difference is that the AS Description information has been omitted. In order to return the ASN Description and additional info, one use:

If a given prefix does not exist in the table, the daemon will return a standard NXDOMAIN response (domain does not exist).
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Simultaneously search thousands of IPs in minutes and gain accurate WHOIS lookup results