Step 1
Proceed to Terminal application.
Step 2
Open /etc/sysctl.conf file on a text editor by entering this code: sudo gedit /etc/sysctl.conf
Step 3
Insert the following lines at the bottom section of the text file:
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
Then click on Save.
*close the text editor after saving.
Step 4
Enter this code at the terminal: sudo sysctl -p
Step 5
Enter this code: cat /proc/sys/net/ipv6/conf/all/disable_ipv6
If you see an output of '1' then IPv6 has been successfully disabled.