STFU && RTFM

I love using command line tools, especially for troubleshooting networking. There are two simple commands you need to know; ipconfig and ping. Here’s a simple guide to finding where the problem :
 

1. Open the command line by opening the “run” dialog box, entering cmd and clicking OK
2. Ensure that the TCP/IP service is running by pinging the loopback address like so: ping 128.0.0.1
3. Run the ipconfig command, which should give you information something like this:

IP Address. . . . . . . . . . . . : 192.168.1.100
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1

4. If your address is not an APIPA address, ping your IP-address.
5. Ping the default gateway
6. Ping www.iana.org
7. Ping the website or server you are trying to reach

 
If any of the above tests fail, you’ve found where the problem is.

Having once again forgotten most of the commands I use in the command shell in Linux in general and Ubuntu especially, I did a quick google search, which turned up this thread at the Ubuntuforums. The thread had two amazingly useful links, both of which referred to quick reference cheat sheets provided by FOSSwire.com Here they are:
 

• Unix/Linux Command Line Reference
• Ubuntu/Kubuntu Command Line Reference