# Module 1: Wireshark Fundamentals

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## Overview

Wireshark is the most widely used network protocol analyzer in the world. It lets you capture packets off a live network interface and inspect them at every layer of the OSI model \u2014 from raw Ethernet frames up through application-layer payloads. Whether you are troubleshooting a DHCP failure, diagnosing slow application performance, or investigating a security incident, Wireshark gives you ground truth. Logs can lie, dashboards can mislead, but the packet capture tells you exactly what happened on the wire.

In a production environment, the ability to read a packet capture separates the engineers who guess from the engineers who know. When a client reports \u201cthe network is slow,\u201d you can fire up Wireshark, capture traffic, and pinpoint whether the problem is DNS resolution delay, TCP retransmissions, TLS negotiation overhead, or something else entirely. This skill is not optional for any serious network or systems engineer.

This module walks you through the Wireshark interface, teaches you how to start and stop captures, apply filters to isolate the traffic you care about, and read the decoded packet fields. By the end, you will have deployed the full lab topology in CML and completed your first captures \u2014 ICMP and DNS \u2014 which lay the foundation for the DHCP deep-dives in Modules 2 through 4.

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## Key Concepts

### What Is Wireshark?
Wireshark is a free, open-source packet analyzer. It captures raw network frames from an interface (physical NIC, virtual NIC, or SPAN port) and decodes them into human-readable protocol fields. It supports over 3,000 protocols and can read/write  and  file formats.
