How to Disable IPv6 on Redhat / CentOS 6 / CentOS 7

This howto will show you how to disable IPv6 on RHEL 6/7, CentOS 6, and CentOS7.

IPv6 is enabled by default. In this article, I summarize 3 configuration which needs to be changed to completely disable IPv6.

Check the configuration of the existing network with the “ifconfig” command. If inet6 appears in the configuration, that means IPv6 is enabled.

Here’s how to disable IPv6 on Redhat / CentOS 6 / CentOS 7:

1. Update /etc/sysctl.conf:

Method 1:

# vi /etc/sysctl.conf

Add the following :

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1

Run the following command to take effect.

# sysctl -p

Method 2:

To disable ipv6 in the running system:

# echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6
# echo 1 > /proc/sys/net/ipv6/conf/default/disable_ipv6

or

# sysctl -w net.ipv6.conf.all.disable_ipv6=1
# sysctl -w net.ipv6.conf.default.disable_ipv6=1

2. Update config file in/etc/sysconfig/network-scripts/ifcfg-eth0 and /etc/sysconfig/network-scripts/ifcfg-ens160:

For CentOS 6:

# vi /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0
HWADDR=00:0C:29:C5:36:7C
TYPE=Ethernet
UUID=f9db89e6-013a-4403-8893-ae0536c6306f
ONBOOT=yes
NM_CONTROLLED=no
BOOTPROTO=static
IPADDR=192.168.0.9
NETMASK=255.255.255.0
IPV6INIT=no

For CentOS 7:

# vi /etc/sysconfig/network-scripts/ifcfg-ens160

TYPE="Ethernet"
BOOTPROTO="static"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="no"
IPV6_AUTOCONF="no"
IPV6_DEFROUTE="no"
IPV6_FAILURE_FATAL="yes"
NAME="ens32"
UUID="ccfd7425-20ab-40c9-a141-b71828a1b8bf"
DEVICE="ens160"
ONBOOT="yes"
IPADDR="192.168.0.100"
PREFIX="24"
GATEWAY="192.168.0.1"
DNS1="8.8.8.8"
DOMAIN="ehowstuff.local"
IPV6_PEERDNS="no"
IPV6_PEERROUTES="no"
IPV6_PRIVACY="no"

3. Edit /etc/sysconfig/network file and add “no” to NETWORKING_IPV6.

# vi /etc/sysconfig/network

NETWORKING_IPV6=no

I would advise you to restart the network configuration as below:

For CentOS 6:

# service network restart

For CentOS 7:

# systemctl restart network

Source : https://wiki.centos.org/FAQ/CentOS6