Unable to find any PTR-records for the specified domain/ip :(
Log
+000
Resolving PTR record of '173.199.56.0'
+242
ERRNo PTR record availible DNS server 'ns1.getgo.com' raised an NotExistentDomain error, while beeing queried for PTR-records on domain '0.56.199.173.in-addr.arpa'.