Book Image

Learn Wireshark, - Second Edition

By : Lisa Bock
5 (1)
Book Image

Learn Wireshark, - Second Edition

5 (1)
By: Lisa Bock

Overview of this book

Wireshark is a popular and powerful packet analysis tool that helps network administrators investigate latency issues and potential attacks. Over the years, there have been many enhancements to Wireshark’s functionality. This book will guide you through essential features so you can capture, display, and filter data with ease. In addition to this, you’ll gain valuable tips on lesser-known configuration options, which will allow you to complete your analysis in an environment customized to suit your needs. This updated second edition of Learn Wireshark starts by outlining the benefits of traffic analysis. You’ll discover the process of installing Wireshark and become more familiar with the interface. Next, you’ll focus on the Internet Suite and then explore deep packet analysis of common protocols such as DNS, DHCP, HTTP, and ARP. The book also guides you through working with the expert system to detect network latency issues, create I/O and stream graphs, subset traffic, and save and export captures. Finally, you’ll understand how to share captures using CloudShark, a browser-based solution for analyzing packet captures. By the end of this Wireshark book, you’ll have the skills and hands-on experience you need to conduct deep packet analysis of common protocols and network troubleshooting as well as identify security issues.
Table of Contents (28 chapters)
1
Part 1 Traffic Capture Overview
6
Part 2 Getting Started with Wireshark
11
Part 3 The Internet Suite TCP/IP
16
Part 4 Deep Packet Analysis of Common Protocols
21
Part 5 Working with Packet Captures

Dissecting a DHCP header

When reviewing a DHCP packet, you will see many fields in the header, as shown here:

Figure 14.6 – DHCP packet structure

To follow along, obtain a copy of DHCP.cap from https://wiki.wireshark.org/uploads/__moin_import__/attachments/SampleCaptures/dhcp.pcapand and open it in Wireshark. Expand the DHCP header in Frame 1, as follows:

Figure 14.7 – A DHCP header

As we can see, each DHCP header contains key fields and identifiers. Let's look at these in more detail.

Examining DHCP field values

Within the header, you will see key fields that help the DORA process move through the various states. The field values are as follows:

  • Operation Code (op): This indicates the message type; for example, 1 = BOOTREQUEST or 2 = BOOTREPLY. In Wireshark, this is displayed as Message type, as shown in the preceding screenshot.
  • Hardware Type (htype): This defines the type of connection for...