Disable IPv6 inet6
/etc/modprob.conf
# Disable IPv6
alias net-pf-10 off
alias ipv6 off
/etc/sysconfig/network
NETWORKING_IPV6=no
ip6tables off
# chkconfig ip6tables off
Reference:
http://ysmt.blog21.fc2.com/blog-entry-173.html
http://www.kajukaju.net/centos/ipv6.php