$> nslookup 212.6.225.4
Note:  nslookup is deprecated and may be removed from future releases.
Consider using the `dig' or `host' programs instead.  Run nslookup with
the `-sil[ent]' option to prevent this message from appearing.
Server:         217.172.166.7
Address:        217.172.166.7#53

** server can't find 4.225.6.212.in-addr.arpa: NXDOMAIN

$>