RHEL6 disable ipv6

Edit /etc/sysconfig/network
Change the following:
NETWORKING_IPV6=yes to NETWORKING_IPV6=no

Add a new file /etc/modprobe.d/ECS.conf containing
alias net-pf-10 off
alias ipv6 off

Stop the ipv6tables service
service ip6tables stop

Disable the ipv6tables service
chkconfig ip6tables off

After these changes, IPv6 will be disabled after the next reboot of your system.

verify ipv6 is disable
lsmod | grep ipv6
ifconfig

netstat

ref.: http://linuxnet.ch/groups/linuxnet/revisions/5b3a1/6/