The dig command is a strong device for troubleshooting queries and responses obtained from the Domain Name Service (DNS). It’s put in by default on many working methods, together with Linux® and Mac OS X. It may be put in on Microsoft Home windows as a part of Cygwin.
One of many many issues dig can do is to carry out recursive DNS decision and show all the steps that it took in your terminal. That is extraordinarily helpful for understanding not solely how the DNS works, however for figuring out if there is a matter someplace throughout the decision chain that trigger decision failures to your zones or domains.
First, let’s briefly overview how a question recursive receives a response in a typical recursive DNS decision state of affairs:
- You because the DNS shopper (or stub resolver) question your recursive resolver for www.instance.com.
- Your recursive resolver queries the foundation nameserver for NS information for “com.”
- The foundation nameserver refers your recursive resolver to the .com Prime-Stage Area (TLD) authoritative nameserver.
- Your recursive resolver queries the .com TLD authoritative server for NS information of “instance.com.”
- The .com TLD authoritative nameserver refers your recursive server to the authoritative servers for instance.com.
- Your recursive resolver queries the authoritative nameservers for instance.com for the A document for “www.instance.com” and receives 1.2.3.4 as the reply.
- Your recursive resolver caches the reply in the course of the time-to-live (TTL) specified on the document and returns it to you.
The above course of principally appears like this:
Step 1
Step 2
Step 3
Step 4
Step 5
This course of happens each time you sort a URL into your net browser or fireplace up your e mail shopper. This illustrates why DNS reply velocity and accuracy are so necessary: if the reply is inaccurate, chances are you’ll must repeat this course of a number of instances; and if the velocity with which you obtain a solution is gradual, then it can make every thing you do on-line appear to take longer than it ought to.
Driving each DNS reply velocity and accuracy is on the core of the IBM® NS1 Join® worth proposition.
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