Using dig +trace to understand DNS resolution from start to finish

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 on your zones or domains. 

First, let’s briefly assessment how a question recursive receives a response in a typical recursive DNS decision state of affairs: 

1. You because the DNS shopper (or stub resolver) question your recursive resolver for www.instance.com. 
2. Your recursive resolver queries the basis nameserver for NS data for “com.” 
3. The basis nameserver refers your recursive resolver to the .com High-Degree Area (TLD) authoritative nameserver. 
4. Your recursive resolver queries the .com TLD authoritative server for NS data of “instance.com.” 
5. The .com TLD authoritative nameserver refers your recursive server to the authoritative servers for instance.com. 
6. Your recursive resolver queries the authoritative nameservers for instance.com for the A file for “www.instance.com” and receives 1.2.3.4 as the reply. 
7. Your recursive resolver caches the reply all through the time-to-live (TTL) specified on the file and returns it to you.

The above course of principally seems to be 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 hearth up your e mail shopper. This illustrates why DNS reply velocity and accuracy are so necessary: if the reply is inaccurate, you could have to repeat this course of a number of instances; and if the velocity with which you obtain a solution is gradual, then it’s going to 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.   

Learn more at IBM NS1 Connect