How can you use packet analyzers to troubleshoot network problems?

1 What is a packet analyzer?

A packet analyzer is a software or hardware tool that intercepts and records the data packets that are transmitted and received over a network. A data packet is a unit of information that contains the source and destination addresses, the protocol, and the payload of a network communication. A packet analyzer can capture packets from different sources, such as a network interface card, a switch port, or a wireless adapter. A packet analyzer can also display the packets in a readable format, decode the protocol headers and fields, and provide statistics and graphs of the network activity.

2 Why use a packet analyzer?

A packet analyzer can be a powerful tool for troubleshooting network problems. It can be used to identify the source and destination of network traffic, measure bandwidth usage and performance, detect and isolate errors, monitor security and compliance of protocols and applications, as well as debug and test the functionality and compatibility of network devices and software. In this way, a packet analyzer can provide valuable insights into the state of your network.

3 How to capture packets?

To capture packets, you need to install and run a packet analyzer on a device that is connected to the network segment that you want to monitor. You also need to configure the packet analyzer to select the appropriate network interface, capture mode, and capture filter. The capture mode determines how the packet analyzer intercepts the packets, such as promiscuous mode, which captures all packets on the network, or normal mode, which captures only packets addressed to the device. The capture filter determines which packets are captured and stored, based on criteria such as protocol, port, address, or content.

4 How to filter packets?

To filter packets, you need to use the packet analyzer's filtering features to narrow down the captured packets to the ones that are relevant to your network problem. You can use two types of filters: display filters and analysis filters. Display filters are applied after the capture and only affect the display of the packets, not the storage. Analysis filters are applied during or after the capture and affect both the display and the storage of the packets. You can use filtering expressions to specify the filter criteria, such as tcp.port == 80 to filter packets that use the TCP protocol and port 80.

5 How to analyze packets?

When analyzing packets, you can use the packet analyzer's analysis tools to examine the details and statistics of the filtered packets. Different views and modes are available, such as the packet list view which provides a summary of each packet, the packet detail view which shows decoded information, the packet bytes view which displays raw data in hexadecimal and ASCII formats, the statistics view which shows aggregated information of the packets, and the graph view which presents a graphical representation of the packets. These views can be used to gain insights into time, source, destination, protocol, length, protocol headers and fields, payload data, number, size, rate, distribution of packets by protocol, address or conversation, throughput, latency or jitter of packets over time.

6 How to use packet analyzers to troubleshoot network problems?

Packet analyzers are powerful tools that can help you troubleshoot network problems by capturing, filtering, and analyzing network traffic. To use them effectively, you need to follow a systematic approach that involves defining the network problem and identifying the possible causes and symptoms, planning the packet capture and selecting the appropriate packet analyzer, network interface, capture mode, and capture filter. Once you start the packet capture, you can reproduce the network problem or observe the network behavior. After stopping the packet capture and saving the captured packets for further analysis, you can apply display and analysis filters to isolate relevant packets and reduce noise. With the analysis tools, you can inspect packet details and statistics to look for clues and evidence of a network problem. Finally, compare the packet analysis with expected or normal network behavior to identify the root cause and solution of the network issue. By using packet analyzers in this way, you can gain insight into the network performance, errors, security, and functionality and solve network issues faster and more effectively.

7 Here’s what else to consider

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