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Wireshark Revealed: Essential Skills for IT Professionals by Charit Mishra, Yoram Orzach, James H Baxter

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Analysing DNS problems

In the previous recipe, we saw how to identify a normal operation of DNS. In this recipe, we will learn how to discover problematic behavior of DNS, and how to figure out its source.

Getting ready

A DNS problem can result in bad performance while browsing the Internet, slow network while working inside the organization network, or any other performance issues. We will see how to isolate these problems and how to find out whether it is a DNS issue or not.

How to do it...

There are two major types of problems in DNS:

  • DNS cannot resolve a name
  • Slow operation of DNS

In both cases, connect your Wireshark to the network in the following order when you suspect an Internet connectivity problem:

  1. First, port mirror the PC of the customer ...

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