When we now stated that the cable is flawless and the link is up between the machines (and switches) we will turn to the next layer in the OSI model, namely the network. The network is the entity connecting our different links on the way between two different machines that might be located in different parts of the world. If you looking at CNN:s home page you will first traverse your own Ethernet and then over your cupper or fiber connection to your nearby telecom station. From there you traverse different links provided by different Network operators until you reach the final fiber and Local Ethernet at the CNN host site.

Every link in the chain represent it's own network with it's own addresses and you can easily trace the route of your traffic to the homepage you are visiting. But back to the trouble shooting. First we need to control that you're machine has the configuration needed. If you starts the network configuration application in your computer (in the control panel in PC:s) and click on the network card you are using you can see what your IP address is. Different cards represent different links and have different IP addresses. You can see you're own IP address and the IP address to the default gateway and name server. The default gateway is where your computer sends all packets that are not located on a connected link (network). On a PC it is also possible to start a command window (cmd) and write the command ipconfig. Then you will see information about all connected links.

When you stated that their is an address and a default gateway you can test reaching the default gateway or other computers on your own network. Start with a command or terminal window where you can write the command ping. Ping is a command that test if you got response on the IP level. Try first Ping localhost to see that your own computer responds on IP. Then try to ping the address of your default gateway. If that work you also know your local Network is OK. If not, try with another known IP address on the LAN to see if it is OK. If everything seems OK you can try to ping your name server (found in the network configuration).

If everything locally works you need to go further out from your LAN. There is a similar command to Ping that is called tracert in Windows (traceroute on mac or unix). Try to tracert to the site name you can't reach, like "tracert www.cnn.com". You will got the resulting response times from one host per line. * means no response. That way you can no see how long way your packet goes before it stops. Certain equipment like firewall's does not respond to tracert, there will be only *. But there might be an answer on the next line anyway. At least you should see your default gateway as this answered on ping on the previous test. If you got an answer with "cannot resolve host" you probably has problem with your name server that should resolve your names to IP addresses. If so, please see the next chapter about network services.

About network services outside the network