So what do you do if you've followed this (and maybe other) home networking guides step-by-step, but still something's not right. Everything works except .... Or everything's been working great for weeks, but now one of the computers can't connect, and you don't know why. This section is dedicated to troubleshooting those pesky network problems. When I started writing this "quick" guide to home networking, which later turned in to the full-length novel it is today, this is the section I was most interested in writing. Network problems are bound to happen given enough time. I play with my home network a lot, so I tend to cause my own problems. (First rule of engineering: If you mess around with something long enough, you will eventually be successful in breaking it.)
These steps are the ones that I follow myself, so I'm certain they can help at least some of you out of a jam. The first time you are bringing up a new home network or adding new device (e.g., computer, XBox 360) to an existing network, it's a good idea to follow the steps in order. However, when troubleshooting a device that had been working you might want to skip right to test 4 or test 5. I don't usually start with test 1 in that case. I start farther down and if a test fails, I work my way backwards towards test 1. After you've done this for a while, you'll get a feel for where to start just by the way the failure behaves, but these steps are always here in case you encounter a problem that resists being solved.
Once the Ethernet ports are installed, it's good to make a quick check that they have been recognized and the drivers are installed. This may not be easy to do with some devices like networked printers (which is fine since those are usually installed and tested at the factory), but for Windows-based PCs, there are some easy tests that can be done. If you can't get similar successful results to those you will see in this section, then your Ethernet card/port/adapter is not properly installed you'll likely just be wasting your time to even try to go on. These tests are simple, but it's also essential that your Ethernet ports pass.
The first test is to just verify that the Ethernet port is recognized by your operating system. The graphics in this section were taken from a mix of Windows 2000, XP and Vista machines. Most were captured using a laptop with Windows 2000 Professional installed on it. In most of the tests, Windows XP and Vista machines have the same tools with a slightly different look. Even if your Windows computer came with an Ethernet port pre-installed or built-in, it's good to make these checks. Occasionally, manufacturers forget to install the drivers for some of their devices and sometimes another driver installed for another device can interfere with the LAN driver. Start by right-clicking on the My Computer icon and choosing Properties from the pop-up menu as shown. (If you don't have a My Computer icon on your desktop and you are running Windows XP, go try the tutorial procedure Displaying the My Computer and My Network Places Icons in Windows XP and then return here.)
In Windows 2000 and XP, the System Properties dialog window will appear as shown below. Next, click on the Hardware tab and then the Device Manager button.
In Vista, the Control Panel -> System Properties dialog window will appear instead as shown below. Next, click on the Device Manager link.
This will bring up the Device Manager dialog window which is roughly the same for Windows 2000, XP, and Vista.
If your Ethernet adapter is recognized as a device by the operating system, it will appear under the Network adapters portion of the Device Manager list. (By default, the devices are listed alphabetically by type.) If you see Network adapters listed, click on the little plus sign next to it to expand that entry. You could see your specific Ethernet card (NIC) listed there as shown below. If you don't see such an entry, see Problem 1: There isn't any entry named "Network adapters" in the Device Manager or there is no entry in the Network adapters that corresponds to my Ethernet adapter. (Note: In the words of the Jedi master, "The 1394 Net Adapter is not the device you're looking for.")
Right-click on the entry for your card (e.g., Linksys EtherFast) and choose Properties from the pop-up menu. (You can also just double-click on the entry.)
The properties for your Ethernet adapter should look similar to the one below. Pay particular attention to the line that reads, "This device is working properly." This is what we want it to read.
The usual culprit when you know you have the Ethernet adapter installed, but it doesn't show up under the Network adapters list is a bad or missing driver. Look in the Device Manager for a Other devices entry. (In general, you should not have any devices listed in the Other devices entry if all devices are installed properly on your PC.) If there is one, expand it by clicking on the plus sign. If you see a device named like "PCI Ethernet Controller," it's almost guaranteed you have a (lack of a) driver problem. Possible solutions:
What you want this field to say is "This device is working properly." If you have any other message there, you likely have a wrong, corrupted, or missing driver. Microsoft has a nice list of the device manager error codes here along with some suggested solutions. At some point, I'd like to add a troubleshooting section here if there is a need for it, but right now, I'd just like to get this finished and available.