How to disable IPv6 on Redhat / RHEL 7

Simply add the following lines to the sysctl.conf file e.g.:

vi /etc/sysctl.conf

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.eth0.disable_ipv6 = 1

(where eth0 is your NIC)

and finally to make the changes permanent run:

sysctl -p