1) Write down your current WAN Ip Address and Default Gateway
-Go Start>Run Type in "cmd" then type the command ipconfig
2) login to your router
-open web browser
-type the default gateway into the web browser(default: 192.168.1.1)
-type in username and password
3) Release Ip
-Go to status and hit dhcp release
You will now not have internet
4)Unplug your modem and your router
5) Wait 5-10 minutes
6) Plugin router - Wait for it to fully load maybe 1 minute
7) Log back into your router and go to status
8) Plugin modem(May take several minutes to start)
9) Once modem is fully connected hit DHCP renew
You should get a new external ip and have internet again .. you can test by visiting a webpage
Check to see if the new ip is different to the one you wrote down earlier by typing "ipconfig" in the command line.