Debugging DNS can be tricky and, in this chapter, we examined the tools that can help us figure out exactly where a problem lies so that we can work toward remedying it.
There are numerous command-line utilities that can help us drill down quickly to find a problem and that come with the added bonus of being able to be incorporated into scripts and automated.
Despite the plethora of web-based DNS tools out there, not all of them are terribly useful, and many are prone to spewing verbose "look busy" output that doesn't actually convey any useful information or assist in debugging actual issues.
We did cover the few truly useful web-based tools that stand apart from the crowd, either in their uniqueness (such as domaintools being the only known historical archive of whois records) or their utility (whatsmydns being very handy for debugging anycast or geo-distributed...