Top 10 Most Overlooked Causes of Trouble in a Cisco Network

Rodger Foster, Global Knowledge Instructor, CCSI, CCNA

Abstract

Today's networks are ever more complex, and they support diverse applications. Troubleshooting techniques are critical, and network technicians need to recognize and repair problems as fast as possible. With the addition of Voice and Video applications, understanding the most overlooked causes of trouble in Cisco Networks will help find the cause of most problems quickly and easily. This white paper is a guide to the top ten causes of trouble in a Cisco network and how to address them. However, it is not intended to be a troubleshooting guide.

1. Not Knowing Where To Start

Getting information from the users is critical in understanding where to start troubleshooting any network problems. Asking questions that will assist in defining the problem is just as important as correcting the problem. Asking the users if what is broken ever worked is one of the biggest causes of trouble network administrators' face. Users will report network issues with an application when all of their troubleshooting has been exhausted, and it is up to the network administrator to glean this information when first contacted by the user. If network administrators do not ask the right questions, it could lead to wasted time troubleshooting perceived network issues that are really not network issues. Network administrators could also cause other network problems while troubleshooting. Problems for other users could result when performing troubleshooting steps that may be unnecessary and do not lead to the cause of the problem.

2. Out-of-Date Documentation

In today's market, organizations are forced to do more with less. When projects are being completed it is imperative to take the time to complete the documentation that goes along with that project. However, there are instances where time is not available to get the documentation completed. When troubleshooting a problem, it is critical to have the proper updated documentation. Having the updated documentation available helps ensure that unnecessary troubleshooting steps are avoided. Proper documentation helps network administrators to focus on where the trouble is.

The following diagram shows a simple network. If a user connected to Switch A reports problems connecting to a device on Switch B, then there is no reason to include the HQRouter in the troubleshooting steps. However, if there were no documentation or the documentation was not up-to-date network administrators could waste time by performing troubleshooting on the HQRouter and add time to resolving the true issue. In this case troubleshooting should be limited to Switch A, Branch, and Switch B.

3. Misunderstanding the Processes

In order to understand possible causes of trouble, a network administrator needs to understand the processes involved in sending and receiving data. There are many hours of troubleshooting time spent on working problems in the network due to lack of process knowledge. Not knowing how a process works can lead to inefficient troubleshooting. An example would be troubleshooting an application issue when the real problem is that there is a wrong IP address assigned to the device who's application is having problems. Almost everything in networking is a process and network administrators that are not aware of those processes are asking for extra unnecessary work. The processes that network administrators need to be aware of are related to the OSI model. Layer two processes are different than layer three processes but knowing these can assist in narrowing the focus of troubleshooting.

4. Complex Designs

In large networks the design can be very complex. When you're in this type of environment it is very easy to make troubleshooting mistakes. Cisco is versatile enough to provide, in some circumstances, many different methods to accomplish the same goal. When methods are not standardized and more than one method is used troubleshooting can become more detailed and involved.

5. Redundant Troubleshooting

Redundant troubleshooting relates to having either more than one network administrator performs the same task or one administrator performs the same task over and over. Although redundant troubleshooting is not a cause of a network problem, it extends the duration of the problem. Good communications skills are essential between network administrators in order to avoid redundant troubleshooting. Two network administrators could be troubleshooting different problems with common devices. For example, two different users report problems connecting to the same application server. This situation should cause network administrators to look to the common denominator, which may be the connection from the network device to the server or the path between the users and the server. By using good communication skills, the two network administrators could decrease the time needed to isolate and correct the problem.

6. Lack of Communication

Some troubles in the network will need to be passed along to others who can continue troubleshooting. In some of these cases some troubleshooting steps may be duplicated due to lack of communications between administrators. This lack of communication can lead to hours of wasted time duplicating efforts and still not lead you closer to resolving the problem. Having a method of turning over problems is very important for administrators who work in networks with a need for 24/7 support. This turnover should be as detailed as possible to ensure that efforts are not duplicated and more focus can be applied to the issue.

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