Identify and correct common network problems

Exam: Cisco 200-301 - Cisco Certified Network Associate (CCNA)

One important section in CCNA exam is “Identify and correct common network problems”. We will now in this chapter discuss the same topic in more details so that you can get a better idea of how to go about preparing for the exam. As a network administrator you will often need to understand and correct the network problems. We are now about to discuss how exactly you can identify the network problems in order to solve them.

Some common network errors that you will often come across are:

Unable to renew the IP address.
Unable to clear the ARP cache
Unable to clear the DNS cache
An operation that was performed on something that is not even a socket

Now that you know the most common problems these are the steps that you must follow in order to solve the problem:

You must ensure that the computer is switched on and it is connected to a network.
The network administrator must know that the windows have a built in capacity to repair a network connection. This is the function that can give a lot of valuable information in the form of an error message. These error messages will look like the following:
- Unable to renew your IP address
- Unable to clear the ARP cache
- Unable to clear the DNS cache
Now let’s deal with each of these error messages one by one. For example “the unable to clear the DNS cache”. This error message means that the DNS client service has been disabled. The following must be taken as a network administrator:
- Open the services MMC plugging which is located under the administrative tools in control panel;
- Now double click it and try to find the "DNS Client";
- You must change the start up type from disable to automatic or manual. After that click apply;
- Now reboot or click start to start the service again;
- Now try to verify what you have done by repairing the connection again.
In this step you must try to fix a problem that came up in the IP address. If the repair process gives an error saying that it has not been able to obtain the IP address. You will need some more information as this is not sufficient enough. This information can be obtained through the command line. How to go about doing that is open a command prompt by going to start. Then go to programs, accessories and then command prompt. Now you will have to type ipconfig/renew to get the ip address from the command line.
You will now have to follow up the error message that will appear. The error message that you will mostly get will be something like this “an operation was performed on something that is not a socket”.
Next step will be to fix this error message. This message basically shows that there is a winsock corruption that happens due to a spyware. To fix this you can run the windows xp sp2 or the windows Vista. The steps followed are start – run – cmd – netshwinsock reset. After this you will have to reboot the computer. You can also download the program to reinstall the winsock.

Cisco says that there is an eight step method to trace the network issues and these steps are:

Define the problem – try to understand from the user what aspect of the computer is not working. This may need patience and good listening skills. It is absolutely fine if you tell the user that you will need some more information before you solve the problem.
Gather the detailed information – at this step you will have to gather all the information that is available. Even if information seems not important that too must be recorded. You can use the tools like ping, network monitor and trace to find the problem. We have discussed these tools in the previous chapters.
Consider the possible cause for failure – you must slowly and calmly try to look at all the points that may cause the failure. It can be as simple as a connectivity issue at sometime and in some cases it can be multiple problems.
Devise a plan to solve the problem–once you have got an idea of what the problems must be you must try to look at the solutions. This will help you to come up with an action plan. The solution must be thought about critically and discussed with experts before you take a decision. A brainstorm session is must before the solution is implemented.
Try to implement the plan – while implementing the solution keep the following points in mind:
- Try to make only one change at one time.
- Try to make those changes first which will have the least impact on the users. These changes are called transparent changes. They are done when there can be multiple reasons for failure in the network.
- Try not to create a security hole as you make the changes. This is very critical as network will often have sensitive information.
- Always keep the possibility of going back on the changes made. This will ensure that you can work better on the network and get the desired results.
Check the results of the implementation–after you have implemented the change and the result is positive. You must keep observing the change. You must also maintain a log of the solution made. This is quite possible that the solution may not work for a long time and you may have to come up with one more solution.
You must repeat the process from step one if the problem is not resolved – if the solution that you thought of did not work you will have to start from the step one again.
Document the change that you made to solve the problem so that the document can be used in the future. You must make a proper file and maintain it.

We hope that this chapter on “Identify and correct common network problems” will help you to get a better idea of what are the problems that you can generally come across in a network. Do keep these points in mind in order to get a deeper and a clearer idea of the problems.

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