Debugging DNS issues can be tricky. There are numerous moving parts to any given DNS lookup, and because they occur under the hood and are abstracted away from the user-facing network functions, you have to know exactly where to look and what to look at to figure out what is happening.
Furthermore, it is not uncommon for users to suspect DNS problems when facing symptoms that are not related to DNS. Getting a "404 Not Found" page when you navigate to a website is not a DNS issue. Yet it is frequently reported as one.
What follows are various tools that can be used to isolate and diagnose issues. First, we'll look at command-line tools, and then at web-based ones.
In this chapter, we will cover the following topics:
- Command-line-based tools:
- Whois
- dig
- named checkzone and named checkconf
- dnstop
- Web-based debugging...