All routing protocol troubleshooting should begin with a logical sequence, or process flow. This process flow is not a rigid outline for troubleshooting an internetwork. However, it is a foundation from which a network administrator can build a problem-solving process to suit a particular environment.

1. When analyzing a network failure, make a clear problem statement.
2. Gather the facts needed to help isolate possible causes.
3. Consider possible problems based on the facts that have been gathered.
4. Create an action plan based on the remaining potential problems.
5. Implement the action plan, performing each step carefully while testing to see whether the symptom disappears.
6. Analyze the results to determine whether the problem has been resolved. If it has, then the process is complete.
7. If the problem has not been resolved, create an action plan based on the next most likely problem in the list. Return to Step 4, change one variable at a time, and repeat the process until the problem is solved.
8. Once the actual cause of the problem is identified, try to solve it.

Cisco routers provide numerous integrated commands to assist in monitoring and troubleshooting an internetwork:

• show commands help monitor installation behavior and normal network behavior, as well as isolate problem areas
• debug commands assist in the isolation of protocol and configuration problems
• TCP/IP network tools such as ping, traceroute, and telnet

Cisco IOS show commands are among the most important tools for understanding the status of a router, detecting neighboring routers, monitoring the network in general, and isolating problems in the network.

EXEC debug commands can provide a wealth of information about interface traffic, internal error messages, protocol-specific diagnostic packets, and other useful troubleshooting data. Use debug commands to isolate problems, not to monitor normal network operation. Only use debug commands to look for specific types of traffic or problems. Before using the debug command, narrow the problems to a likely subset of causes. Use the show debugging command to view which debugging features are enabled.

Web Links Troubleshooting EIGRP http://www.cisco.com/en/US/tech/ tk826/tk365/technologies_ tech_ note09186a0080094613.shtml