How to find out all IP ranges belonging to a certain AS?

I want to know what IP ranges are belonging for example to the AS714.

How do I get this information?

I know how to do the reverse way, which is easy with whois. But the other way doesn't seem to be that easy.

Solution 1:

They're listed online with related details at http://ipinfo.io/AS714 (replace the ASN to get the equivalent details for any other ASN).

If instead of browsing them you'd rather grab them programmatically you can use the RADb whois server:

$ whois -h whois.radb.net -- '-i origin AS714' | grep -Eo "([0-9.]+){4}/[0-9]+" | head
17.108.0.0/16
17.106.0.0/15
17.102.0.0/16
17.207.0.0/16
17.216.0.0/16
17.250.48.0/24
17.252.65.0/24
192.35.50.0/24
17.148.0.0/14
17.86.0.0/17

Solution 2:

Ok, I just found one simple way. You just put this http://bgp.he.net/[ASXXX]#_prefixes in your browser, where [ASXXX] is a certain AS and a number like this http://bgp.he.net/AS714#_prefixes.