Can refresh the network connection without rebooting the system, Open the Command Prompt,

Go to Programs > Accessories > Command Prompt. Or, click "Run" under the start
or
press "Windows Key" + " R ",
or
If you are using Windows 8 Right click on "Windows Icon" at left bottom, choose "Command prompt" or "Command Prompt(Admin)"



Then enter the ipconfig command, will shows IP address configuration details,

"ipconfig"

In the command prompt just type the following command and hit the enter. 

 "ipconfig /release"

 "ipconfig /renew" 

 "exit"