Disable IPv6

1. Edit the Grub config. 
 sudo nano /etc/default/grub 
 2. Append/edit the following line. 
 GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" GRUB_CMDLINE_LINUX="ipv6.disable=1" 
 3. Update Grub. 
 sudo update-grub 
 4. Reboot for the changes to take effect immediately. 
 sudo reboot now