This post guides you on how to disable IPv6 on CentOS 6 / RHEL 6.
Edit the /etc/sysctl.conf file.
vi /etc/sysctl.conf
Put the following entry to disable IPv6.
net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1
Execute the following command to reflect the changes.
sysctl -p
That’s All.
According to https://www.centos.org/forums/viewtopic.php?t=7989 and point 5 in http://wiki.centos.org/FAQ/CentOS6 this is a deprecated method and breaks selinux amongst other things.