User Guide

49
Chapter 4. Capturing Live Network
Data
4.1. Introduction
Capturing live network data is one of the major features of Wireshark.
The Wireshark capture engine provides the following features:
• Capture from different kinds of network hardware (Ethernet, Token Ring, ATM, ...).
• Stop the capture on different triggers like: amount of captured data, captured time, captured number
of packets.
• Simultaneously show decoded packets while Wireshark keeps on capturing.
• Filter packets, reducing the amount of data to be captured, see Section 4.12, “Filtering while capturing”.
• Capturing into multiple files while doing a long term capture, and in addition the option to form
a ringbuffer of these files, keeping only the last x files, useful for a "very long term" capture, see
Section 4.10, “Capture files and file modes”.
• Simultaneous capturing from multiple network interfaces.
The capture engine still lacks the following features:
• Stop capturing (or doing some other action), depending on the captured data.
4.2. Prerequisites
Setting up Wireshark to capture packets for the first time can be tricky.
Tip!
A comprehensive guide "How To setup a Capture" is available at: http://wiki.wireshark.org/
CaptureSetup.
Here are some common pitfalls:
• You need to have root / Administrator privileges to start a live capture.
• You need to choose the right network interface to capture packet data from.
• You need to capture at the right place in the network to see the traffic you want to see.
• ... and a lot more!.
If you have any problems setting up your capture environment, you should have a look at the guide
mentioned above.