The easy way: if you use Firefox, you can just disable IPv6 in Firefox. Type about:config and search for:
and toggle it to TRUE.
The 'hard' way: disable IPv6 system-wide: you must edit the GRUB. Be very careful, and edit it correctly or else your system might not boot!
1. Open a terminal and type the following command (if you don't use Gedit, replace it with your text editor such as Kate, etc).
sudo gedit /etc/default/grub
2. And search for this:
Modify it so it looks like this:
3. Now, let's update the GRUB:
Or if you don't use GRUB 2, do:
4. And finally, restart your system.