DNS on Windows Server 2003, 3rd Edition

Is nslookup a Good Tool?

Much of the time you’ll use nslookup to make queries in the same way the resolver makes them. Sometimes, though, you’ll use nslookup to query other name servers as a name server would. Which one you emulate will depend on the problem you’re trying to debug. You might wonder, “How accurately does nslookup emulate a resolver or a name server? Does nslookup actually use the Windows resolver library routines?” No, nslookup uses its own routines for querying name servers, but those routines are based on the resolver routines. Consequently, nslookup’s behavior is very similar to the resolver’s behavior, but it does differ slightly. We’ll point out some of those differences. As for emulating name server behavior, nslookup allows you to query another server with the same query message that a name server would use, but the retransmission scheme is quite different. Like a name server, though, nslookup can perform a zone transfer to pull a copy of a zone’s data. So nslookup does not exactly emulate either the resolver or the name server, but it does emulate them well enough to make a good troubleshooting tool. Let’s delve into those differences we’ve alluded to.