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In The Lab
PC Troubleshooting Part 3: Network Troubleshooting
by chris

Troubleshooting a networking problem is probably one of the more frustrating projects you can take on. The main reason for this is that there are so many variables, any one of which could prevent network communication from taking place. I'm not trying to go all technical on you now, but there are "layers" to networking communication. To troubleshoot networks, you will need to eliminate as many of the higher layers as possible and start by checking the basic functions first.

STEP ONE: DEFINE THE PROBLEM

Whether you are troubleshooting a wired network or a wireless one, the approach should be the same. Disable or eliminate as many of the advanced features and settings as possible and begin with just the connection or core settings. This means that before you can configure or test your network connection you need to make sure that Firewalls are (temporarily) disabled and any hardware security features are turned off, such as MAC filtering in the routers and WEP or WPA encryption when testing wireless networks.

STEP TWO: IDENTIFY A POSSIBLE CAUSE and STEP THREE: RESEARCH THE PROBLEM

An example of a wired network problem might be that systems attached to a home network do not show up in "Computers near me" or "Network Places." Any number of network related issues could cause this, and more information would be helpful in isolating the cause. For example, if your network is connected to the Internet through a cable or a DSL always-on connection, can all systems access the Internet? If so, this means that the network hardware is working, and that TCP/IP protocols are installed and some network communication is already occurring. This also means that the problem originates at a higher level. The problem could be caused by certain settings within the protocol properties, blocking at the router, or something as simple as a failure to have a computer on the network manage the local communications. To isolate the problem, you will need to test these different aspects to either eliminate or identify them as part of the problem.

To test the hardware layer of a wired network, make sure the LED indicators on the network adapter are lit, indicating an active network connection. Verifying a wireless connection can be a bit tricky, if only because you must rely on the operating system or wireless software to let you know when connections are made. Don't overlook the obvious when troubleshooting wireless networks; many new notebook computers come with built-in WiFi networking, but have a feature that allows you to disable the antenna or transmitter with a single button or function key combination. The wireless adapter is still enabled, but you will not be able to communicate to anything until the antenna is active again. In this situation, Windows will report that no wireless connections are available.

After hardware connections, the next layer is the software that allows the network adapter to communicate with the operating system. Check the drivers in Device Manager or network properties to make sure that the network adapter is showing up and not reporting conflicts or problems. If no conflicts or issues appear in the Device Manager, then the next thing to check will be protocol and other network items (identified as clients, services or protocols).

Under Windows XP, open the network connections, then right click on your Local Area Connection and select properties; you should find a list that includes items like:

  • Client for Microsoft Networks
  • File and Printer Sharing for Microsoft Networks
  • Internet Protocol (TCP/IP)

If TCP/IP protocol is loaded, then the next thing to check is the properties for this protocol. Under Windows, the "default" settings are to obtain an IP address automatically. If Windows cannot detect a system supplying it with an IP address, it will probably "make one up;" this feature is an "Alternate private IP address."

In a network where you are using a router to communicate to the Internet, all of your local computers still must have unique IP addresses, but they should also all be in the same range. If your router assigns an address range of 192.168.1.xxx, then the address that your computer gets assigned should be something like 192.168.1.123 or 192.168.1.2, etc. If you are not receiving an appropriate IP address, then you can manually assign one. You will also need to include the router's IP address as the gateway address to be able to access the Internet.

If you can connect to the Internet using your browser, get email, but still cannot see other computers on the local network, then you need to check for things like a Firewall on your computer or the computer you are trying to connect to. Other reasons systems may not show up in the "Computers near me" list could be that they are not sharing any resources, or do not have the printer and file sharing enabled.

With network troubleshooting, you will find the line between step 2 and 3 to be somewhat blurred, only because you may have to test each portion of the network configuration to isolate the problem. You will constantly find yourself in the "research" stage, even if this is nothing more than moving back and forth between systems to make sure that IP address are similar, Workgroup names match, and that some basic communication can occur.

STEP FOUR: SELECT AND TEST SOLUTIONS

Selecting and testing solutions also tend to flow into this identification process, simply because you must verify or may change configurations as part of the elimination steps. Unless there is a physical failure like a bad adapter or cable, you will probably be able to identify the reason as you check each part of the different Network configuration properties. Once you identify the specific cause, whether it be a firewall or hardware configuration issue, work your way through the settings to get these security programs back online.

Next month, Chris dives into extreme case modding.

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