Unable to find any PTR-records for the specified domain/ip :(
Log
+000
Resolving PTR record of '168.225.21.0'
+211
ERRNo PTR record availible DNS server 'arin.authdns.ripe.net' raised an NotExistentDomain error, while beeing queried for PTR-records on domain '0.21.225.168.in-addr.arpa'.