Kali/IPv6

disable ipv6

temporarily

sysctl -w net.ipv6.conf.all.disable_ipv6=1
sysctl -w net.ipv6.conf.default.disable_ipv6=1
sysctl -w net.ipv6.conf.lo.disable_ipv6=1

permanently

echo "sysctl -w net.ipv6.conf.all.disable_ipv6=1" >> /etc/sysctl.conf
echo "sysctl -w net.ipv6.conf.default.disable_ipv6=1" >> /etc/sysctl.conf
echo "sysctl -w net.ipv6.conf.lo.disable_ipv6=1" >> /etc/sysctl.conf

enable ipv6

temporarily

sysctl -w net.ipv6.conf.all.disable_ipv6=0
sysctl -w net.ipv6.conf.default.disable_ipv6=0

permanently

Edit /etc/sysctl.conf and remove the lines that disabled IPv6.