LPI Linux Certification in a Nutshell, 2nd Edition

Objective 2: Advanced Network Configuration and Troubleshooting

For this Objective, make sure that you focus on troubleshooting, not just knowing the names of commands. By troubleshooting, we mean being able to:

• Use the applications and configuration files discussed earlier in the chapter

• Review configuration files for simple problems (e.g., misspellings and mis-entered lines)

• Review log files for problems

• Generally keep your cool when faced with balky systems

Although the LPI Exams don't really test you on the last item, we assume that many people reading this book are using it to learn essential Linux skills, as the LPI Exam examines real-world knowledge.

This section contains scenarios that help you learn more about the depth of troubleshooting skills you will need. We'll cover practical uses of netstat, tcpdump, ethereal (and the associated tethereal application), lsof, and netcat (nc). It is also important for you to understand ping and the utilities shown earlier in this chapter in a troubleshooting situation. But we'll start with one of the most basic utilities in networking.

Simple Connectivity Example: Telnet

Suppose an employee reports that the intranet web server is unavailable. What do you do? Open up a web browser? That won't provide much more informaiton than the employee already told you. Instead, try Telnet. Don't get incredulous—Telnet is a terrific troubleshooting tool.

Depending on your location, you can use Telnet to log in to the system and check the process ...