Intermediate - Advanced Level Users.
This book describes the best of the freely available tools for debugging and troubleshooting.
You can start with a lesser-known version of 'ping' that diagnoses connectivity problems, or take on a much more comprehensive program like MRTG for graphing traffic through network interfaces. There's 'tkined' for mapping and automatically monitoring networks and Ethereal for capturing packets and debugging low-level problems.
This book isn't just about the tools available for troubleshooting common network problems. It also outlines a systematic approach to network troubleshooting: how to document your network so you know how it behaves under normal conditions, and how to think about problems when they arise, so you can solve them more effectively.
