"Don't stand chattering to yourself like that," Humpty Dumpty said, looking at her for the first time, "but tell me your name and your business."
"My name is Alice, but—"
"It's a stupid name enough!" Humpty Dumpty interrupted impatiently. "What does it mean?"
"Must a name mean something?" Alice asked doubtfully.
"Of course it must," Humpty Dumpty said with a short laugh . . .
To be proficient at troubleshooting nameserver problems, you'll need a troubleshooting tool to send DNS queries, one that gives you complete control. We'll cover nslookup in this chapter because it's distributed with BIND and with many vendors' operating systems. That doesn't mean it's the best DNS troubleshooting tool available, though. nslookup has its faults—so many, in fact, that it's now deprecated (geekish for "officially out of favor") in the BIND 9 distribution. We'll cover it anyway because it's pervasive. We'll also cover dig, which provides similar functionality and doesn't suffer from nslookup's deficiencies.
Note that this chapter isn't comprehensive; there are aspects of nslookup and dig (mostly obscure and seldom used) that we won't cover. You can always consult the manual pages for those.
Much of the time, you'll use nslookup to send queries in the same way the resolver sends them. Sometimes, though, you'll use nslookup to query other nameservers as a nameserver would instead. The way you use it will depend on the problem you're trying to debug. ...