Debug network performance problems with an open-source network sniffer

If your network is slow or experiencing other problems, one tool to help figure out what's wrong is a network sniffer (also called packet analyzer). Some free multi-platform network sniffers include Ettercap, ngrep, tcpdump, and Wireshark. To get started with network sniffers, Wireshark is a good place to start, as it has fairly extensive documentation and support, and features both GUI and command-line style interfaces. If you want to use Wireshark, don't go to www.wireshark.com. The address is www.wireshark.org.