Post describes procedure to disable IPv6 on CentOS/RHEL 6. There are 2 ways to do this :
1. Disable IPv6 in kernel module (requires reboot)
2. Disable IPv6 using sysctl settings (no reboot required)
Method 1 : using /etc/modprobe.d/ipv6.conf
1. Check if IPV6 is enabled:
# ifconfig |grep inet6 inet6 addr: fe80::d6be:d9ff:fe99:5a77/64 Scope:Link inet6 addr: fe80::d6be:d9ff:fe99:5a77/64 Scope:Link
2. Create /etc/modprobe.d/ipv6.conf if not already present with below parameter:
options ipv6 disable=1
3. Disable ipt6tables service
# chkconfig ip6tables off
4. Reboot the server
# shutdown -r now
5. Confirm if IPV6 is disabled:
# ifconfig |grep inet6 #
Method 2 : Using /etc/sysctl.conf
1. Append below line to the file /etc/sysctl.conf.
# IPv6 support in the kernel, set to 0 by default net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1
2. To make the settings affective, execute :
# sysctl -p