Almost anyone who has managed domains has run into a situation where something has gone wrong with their DNS. We often get support requests in these situations and turn to trusted tools for diagnosing what's going on. In this post, we're going to look at a few tools that are often consulted by people trying to figure out what's going on with their DNS resolution.
dig
Short for Domain Information Groper, dig is a network administration tool for querying DNS name servers. dig defaults to querying for DNS results according to your computer's network settings. It is also capable of querying specific name servers and even of tracing through the resolution of a particular query.
dig has a lot of functionality. Largely because of the vast functionality and reliability of dig, we recommend it over the other local tools available; however, it's still useful to know about other tools that may be available to you.
nslookup
One of the oldest tools for DNS lookup is nslookup. This tool is available on all major operating systems and is quite well known. On some platforms, nslookup is deprecated, but in 2004, release notes for version 9.3.0 of BIND declared it was "no longer to be treated as deprecated."
Unlike other lookup tools, nslookup does not use the local resolver provided by the operating system, but uses its own internal resolver to make DNS queries. This results in some inconsistent and sometimes confusing behavior. Despite its age and notoriety, we at DNSimple don't recommend nslookup for regular use.
host
host is usually used for converting domain names to IP addresses and the other way around. Considered a simple and quick utility, host doesn't have a lot of functions. Though simple, host can be used for reverse lookups as well as DNS queries via IPv6 networking.
Web-based DNS lookup tools
Local DNS lookup tools are important elements of network maintenance. However, they are not the only means of troubleshooting DNS issues. Web-based DNS lookup tools often use the same technologies, but can provide checks on resolution from other networked points and can often give a broader view of the status of a domain than what you would be able to obtain on your own network.
intoDNS
intoDNS allows the user to enter a single root domain name from which the tool then compiles a report on the status of various aspects of the DNS for that zone. intoDNS simplifies many of the results of several DNS query tools into a checklist of things that could go wrong and indicates things that might be worth fixing about your DNS settings. It is optimized for checking mail settings and simple website setups.
MxToolbox
MxToolbox is another tool optimized for checking the status of email related DNS records. It provides both a simple check of MX records as well as a more detailed report on various things to be addressed about a domain's email settings. It is also capable of checking whether a domain or associated IP addresses have been blacklisted from sending mail on various well known lists.
DNSInspect
DNSInspect provides a very similar service to intoDNS, but adds in an overall ranking with a letter grade based on what it finds. DNSInspect also provides a bit more information about how to fix the problems it finds, including external links to support articles where applicable.
What's My DNS
What's My DNS is a great free tool that allows the user to test the global propagation of records set on any zone. This free tool can be very useful in determining whether bad values have been cached with regional ISPs or for inspecting whether records are propagating as expected. By providing a simple checkmark for positive results and a red 'x' where a lookup fails, it's possible to get a truly global view of the status of your domains.
Hopefully this overview has proven useful, but if you've found it in any way overwhelming, don't worry. We use many of these tools regularly and are happy to help you with troubleshooting issues with your domain. Feel free to contact us with anything that you run into on your domains.
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Joseph Caudle
Teacher of people and computers. Fond of subtle distinctions.
