Almost all computers in a home or office are connected to a network. And, in most cases, they are connected with a wire or wireless to a router. The router creates a network called the Local Area Network. All the computers on this network get their IP address from the router. In regards to computer network troubleshooting, the first thing we do is check if all the computers on the network have an IP address, and if each computer be reached through the network?
Before we use the commands to get the data, we check all the connections. If the computer is connected to the router with a cable, then the LED lights near the LAN socket should be either:
The green light should be on all the time
Figure 1: LAN socket with green LED on.
The amber light should flash (this indicates data communication between the computer and router).
Figure 2: Amber LED light flashing indicates data communication.
The router should have a yellow LED light flashing.
Figure 3: The LED light on the router should flash, indicating a connection.
First, we see if our computer has an IP address. We shall start from this step most of the time.
Go to start in the search box and type in cmd, and then in the window, type in ipconfig.
Figure 4: Data given by an ipconfig command.
This will give all the information we need now and will show the IP address. Usually it will be 192.168.1 (a three digit number) like 192.168.1.122. The subnet mask almost always will be 255.255.255.0. The default Gateway will be 192.168.1.1 or 192.168.2.1, depending on the router type. The router also has its own IP address, in which the number goes into the computer network configuration as a gateway.
If there is no IP shown or the IP is 169.xx.xx.xx, then there is no connection between the router and computer, or the router is not working properly. Of course there will be no Internet connection either.
Figure 5: Ipconfig shows 169.254.77.252
This way we can check that all the connected computers are reachable through the network. For this purpose, there is a command PING. For example, a ping 192.168.1.1 will check if we can reach the router. And, this will give some information on the screen, but the important information is Lost = 0, this means we received packets with no loss, and the connection is perfect.
Usually, problems arise when the computers have different operating systems. Even with a Windows operating system, different versions which are sharing the network or printer may not work without some settings tweaked.
Windows Vista, by default, does not allow file sharing with a computer on the LAN network. This is the same with Windows 7; we must go and change the settings in the Network and Sharing Centre in the Advanced Settings. Windows XP does not restrict sharing, but we need to choose the directory and printer that needs to share. This is probably because of higher security on the recent Windows programs, but sometimes even this does not help to protect the network as well as the computers.
The IP address always will be assigned to the computer, and it does not depend on the network or LAN type that the computer is connected to the router by, to another computer, or directly to the Internet.
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