NSLookup is an internet utility to get domain's DNS information. It will help you to find the target IP address of a domain or see what name servers are set on a specific domain.
NSLookup for iPhone and iPad allows you to see the public DNS records of domains or sub domains. Then you may also query the NS and CNAME records. It's also possible to force it to get an authoritative response from main DNS server of the domain.
This advanced version does not have any advertisement.