CentOS 7: Disable IPv6

21st August 2017 LEMP

Check

ifconfig -a | grep inet6
        inet6 fe80::211:aff:fe6a:9de4  prefixlen 64  scopeid 0x20
        inet6 ::1  prefixlen 128  scopeid 0x10[host]

1. Append below lines in /etc/sysctl.conf:

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

NOTE : To disable IPv6 on a single interface add below lines to /etc/sysctl.conf :
net.ipv6.conf.[interface].disable_ipv6 = 1 ### put interface name here [interface]
net.ipv6.conf.default.disable_ipv6 = 1

2. To make the settings affective, execute :

sysctl -p

NOTE : make sure the file /etc/ssh/sshd_config contains the line AddressFamily inet to avoid breaking SSH Xforwarding if you are using the sysctl method

3. Add the AddressFamily line to sshd_config :

# vi /etc/ssh/sshd_config

....
AddressFamily inet
....

Restart sshd for changes to get get effect :

systemctl restart sshd