# Temporary 
sudo sysctl -w net.ipv6.conf.all.disable_ipv6=1
# Permanent
sudo echo "GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX ipv6.disable=1"" | sudo tee -a /etc/default/grub
vim GRUB_CMDLINE_LINUX="... ipv6.disable=1"
# BIOS
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
# UEFI/EFI
sudo grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg

sudo echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf
sudo echo "net.ipv6.conf.default.disable_ipv6 = 1" >> /etc/sysctl.conf
sudo sysctl -p
sudo nmcli connection modify eth0 ipv6.method disabled
sudo tee /etc/NetworkManager/conf.d/99-disable-ipv6.conf <<EOF
[connection]
ipv6.method=disabled
EOF