Troubleshooting Networking Errors

Diy-Computer-Repair can help!

You will find more Troubleshooting techniques in the Self Computer Repair Unleashed! Manual.

Troubleshooting networking errors can be daunting.

Normally if you have a problem you start with the easiest to fix and work your way outward to the hardest so we start with the software, the parameters.

Note: I am assuming you know the network address range of your local network i.e.: 10.10.10.xx (where xx is the node assignment number for each device)

Before we begin I need you to think: Did it work the last time it was powered up? If so, what has changed since then? Did you add or remove a component? Did you change the parameters on a device to make another device work?

If you answered yes to any of the above questions then you need to go back and change it back to the original state. Think about the reason for doing the modifications...

If you answered no to above questions then we need to get to work finding the problem.

Network cards have two LED's one is the 'Link' led (Amber) and the other is the 'Activity' led (Green).

If the link led is off or blinking then you have a connection problem. That is the connection either the card, the network cable, or the network node is having a problem holding the link to the other end of the connection. Check the parameters for the link speed and duplex, if correct next check the cable, disconnect from the network card and reconnect. If the light is still blinking check the other end where it connects. If it is still blinking you could try changing out the network cable. If the light is still blinking try changing the node where the cable connects on the switch or hub. Last thing would be to try another network card in the computer.

If the link light is solid and the activity led does not indicate any activity (it should blink in relation to how much activity there is on the network, idle (no program activity such as a web browser or file transfer) it should blink intermittently - 10 - 100 times a second. If it does not blink then you have a software parameter that is not correct.

We will start with the software, that is the parameters for the network on the effected device. First if it is a computer bring up the command prompt, type in ipconfig then press enter, do you have an IP, subnet mask, and gate way?

Note: These are invalid addresses: 0.0.0.0 and 192.168.1.1 (the 192.168.1.1 is MS way of saying it can not find a DHCP server).

We need more information from ipconfig, type in ipconfig /all this will display more information like: the DNS server and WINS server your computer attaches to for name resolution and so forth.

Before we go to far this information is very important, you should copy it to a text file. If you right click on the top bar of the command window you will get a menu, go to the edit option, then select 'Select all'. Once all the information is highlighted go back to the edit menu and select 'Copy'. Open a text editor, I use notepad, and then paste the information in it. You may want to save the file to the desktop incase you have to restart or shut the computer down.

Is the device a DHCP enabled or does it use a Static IP?

• If it is DHCP we can check the server connectivity by typing in ipconfig /release then type in ipconfig /renew (note the space between ipconfig and the / ). If the IP is the same or changed but not 0.0.0.0 or 192.168.1.1 and both the subnet mask and the gateway are the same as the original ipconfig display then your are connecting to the DHCP server and the problem lies else where.



• If the IP is static then you will have to use a different tactic to find out if the computer is communicating with other devices on the network. You will need to know the name or IP of another device on the network. At the command prompt type in ping computername or IP ( ping mycomputer or ping 10.10.10.10 ) or you can ping the gateway from the ipconfig query earlier. Did you get a reply? Normally on a local network a reply will be less than 1ms and will also list a TTL (Time To Live) for the packet you sent to the target device. If you did not receive a reply (Ping request could not find host) then the problem may be in the IP address.

• From the command prompt ping the name of effected computer or the IP if you know it. Did you get a reply? Did it fail to respond? The TTL - 1ms to 10ms or longer? If the ping came back and the TTL is relatively short then the connectivity is good. If the ping failed to find the effected computer then we need to dig a little deeper.
• Did you receive a ping return from the effected computer? Then the problem is somewhere else.
• If you did not receive a ping from the effected computer we need to look at the properties of the NIC in the computer.

Before going into the properties of the effected computer you can try this: If there is another computer close by and not being used you could take the network cable from that computer and plug it into the effected computer and retry the ping test. Plug the effected computers network cable into the known good computer, is it still able to communicate? Yes then it is not the cable, no, the cable is at fault. If it passes then it is either the NIC parameters or the NIC itself.

Let us assume that the 'swap network cables' didn't make any difference and you still don't get a ping from the effected computer. You now know that the network cable is good and anything from network is getting to the effected computers network node and cable.

Note: The following procedures assume that the computer in question is NOT a server.

To get to the properties of the network card right click on 'My Network Places' go to properties, a new window will open, in the window will be your network card, New Connection, and maybe a Dial up connection or VPN. We are looking for the 'Local Area Connection' Right click on the icon, a menu will open, go to properties.

• The first window will show you the status of the network card and the protocols loaded for that card. If there is a physical problem with the network card then there will be a red circle with a slash over the network card icon in the window labeled 'Connect using:' if this is true then the following procedure is of no use go to Troubleshooting failed devices'
• What we are interested in is the line called 'Internet Protocol (TCP/IP). Highlight the line and click on the 'Properties' button.
• A new window will open. If the radio button for 'Obtain an IP Address automatically is on then then your problem lies elsewhere go to 'Advanced'. If the radio button 'Use the following IP address:' is on then you should see the following items in the windows:
  Note: the IP addresses I am using are factitious.
  

• 
  and you should see:
  
  Use the following DNS server addresses:
  
  

Next click on the 'Advanced' button.

• The first tab is the Settings for the IP, Subnet mask, and gateway. In the gateway window you will see the gateway address and 'Metric'. If your network card is connected directly to the switch/hub and not through a node in the wall or a Wireless share point leave on automatic. If your computer is connected through a node in the wall or a Wireless share

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  point highlight the line and press the edit button, remove the check mark on the 'Automatic metric' and insert a number in the window, I use the number one, the way to figure this out is increment the number one time for each two hops the signal takes. A hop is from the connection to another connection to the final destination. Your computer is connected to a node, one hop, the node is connected to the hub, second hop. Because all computer NIC's should be set this way a number 1 should suffice for the metric. Click ok.
• On the DNS tab, you are interested in the 'DNS server address, in order of use:
• You should have at least one server IP here. The rest of the information can be filled in but is not necessary for your problem resolution.
• Next click on the WINS tab: you are interested in the Wins addresses in order of use. You may or may not have any IP address assigned here. If you have the radio button 'Enable NetBIOS over TCP/IP' clicked then you need a server address that has the WINS Service installed and activated. If you don't know if the WINS Service is installed and activated on a server you can leave the top window blank and click on 'Disable NetBIOS over TCP/IP. You can look at the text file you created when you started this process to see if there is a WINS server on your network. I have found that mis-configuring the WINS tab is the biggest problem with connecting to a network as far as parameters are concerned.
• The last tab Options should be left at Default setting unless you have a Network Administrator that has written rules for a router and has instructed you on what to add/remove/change!

Link Speed and Main Duplex

The network card has some features or options you can set. At the top of the properties page under General is the network card, next to the name of the card is a button 'Configure...'. Open the configuration page, then go to the 'Advanced' tab. The main line you are looking for is the Link Speed / Main Duplex or  Media type (these may be two separate lines: Link Speed and Main Duplex or maybe just Speed and Duplex).

• Most DSL/Cable modems are set for 10MBPS and Full Duplex. The small business or home router such as the Linksys DSL./Cable modem router connect at 100MBPS/Full Duplex. Most network switches and hubs are also 100MBPS/Full Duplex, although the 1GBPS are getting cheaper and you may have one. Newer computers and network cards are in the GMBPS range and sometimes the 'Auto Negotiate' function does not work properly so setting the Link Speed/Main Duplex to the speed of the device you are connecting to may resolve your problem.
• If you are having connection problems then this is a property you will need to look at the symptom.

Some of the symptoms of a speed/duplex problem are -

• Slow connection and transfer
• Connection dropping and reconnecting frequently
• No connection at all

Once you have verified the parameters are correct then try the ping test again. If it passes you have fixed it. If it fails then you have more work to do.

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