How do I disable the IPv6 protocol?

Red Hat Enterprise Linux 4 has Internet Protocol Version 6 (IPv6) enabled by default. In certain situations, it may be desirable to disable IPv6.

To do this, first remove this line from /etc/modprobe.conf if this line exists. (Most Red Hat Enterprise Linux systems will not have one).

alias net-pf-10 ipv6

Next, add the following line to /etc/modprobe.conf:

alias net-pf-10 off

Reboot the system. IPv6 support should now be disabled.

To re-enable IPv6, simply remove the alias net-pf-10 off line from /etc/modprobe.conf and reboot the machine.

UPDATE: the ipv6 still it’s not disabled, so we continue with:

Add to /etc/sysconfig/network file:
NETWORKING_IPV6=no

/etc/sysconfig/network-scripts/ifcfg-XXXXX file;
IPV6INIT=no