| Overview

A router learns about routes to destination networks using a dynamic routing protocol, or by manually configured static routes. The router very likely will use a combination of dynamic and static routing to discover routes. Regardless of the method used, when a router determines that a route is the best path to a destination, it installs that route in its routing table. This module will describe methods for examining and interpreting the contents of the routing table. Network testing and troubleshooting are perhaps the most time consuming components of every network administrator’s job. Efficient testing and troubleshooting must be done in a logical, orderly, and well-documented fashion. Otherwise, the same problems will reoccur, and the network administrator will never truly understand the network. This module describes a structured approach to network troubleshooting and provides some tools to use in the troubleshooting process. Routing problems are among the most common and difficult for network administrators to diagnose. Identifying and solving routing problems may not be simple, but many tools exist that can make the task easier. This module will introduce several of the most important of these tools and provide practice in their use. Students completing this module should be able to: Use the show ip route command to gather detailed information about the routes installed on the router Configure a default route or default network Understand how a router uses both Layer 2 and Layer 3 addressing to move data through the network Use the ping command to perform basic network connectivity tests Use the telnet command to verify the application layer software between source and destination stations Troubleshoot by sequential testing of OSI layers Use the show interfaces command to confirm Layer 1 and Layer 2 problems Use the show ip route and show ip protocol commands to identify routing issues Use the show cdp command to verify Layer 2 connectivity Use the traceroute command to identify the path packets take between networks Use the show controllers serial command to ensure the proper cable is attached Use basic debug commands to monitor router activity