How to disable IPv6 on CentOS / RHEL 5

This post describes steps on how to disable IPv6 function in CentOS / RHEL 5. There are two cases to be considered here while disabling IPv6.
1. With Bonding interface
2. Without Bonding interface

Case 1 : Without Bonding interface

1. The easiest way to disable IPv6 functions is to forbid from loading ipv6.ko module. Thus add one line below onto /etc/modprobe.conf to forbid to install ipv6.ko module onto your kernel:

# vim /etc/modprobe.conf
install ipv6 /bin/true

2. Reboot the server.

# sutdown -r now

Case 2 : With Bonding interface

1. In this case, it is impossible to forbid to install ipv6.ko onto kernel, since bonding.ko needs ipv6.ko. To forbid ipv6 from working actively even when ipv6.ko is loaded, add a line in /etc/modprobe.conf:

# vi /etc/modprobe.conf
options ipv6 disable=1

2. Add a line onto /etc/sysconfig/network:

# vi /etc/sysconfig/network
NETWORKING_IPV6=no

3. Disable ip6tables service:

# chkconfig ip6tables off

4. Reboot the server.

# shutdown -r now