centos 7 disable ipv6

steps

1. method 1

   1. disable all nic

       $ nano /etc/sysctl.conf
       ...
       net.ipv6.conf.all.disable_ipv6=1
       net.ipv6.conf.default.disable_ipv6=1
       ...
      

   2. disable special nic

       $ nano /etc/sysctl.conf
       ...
       net.ipv6.conf.eno1.disable_ipv6=1
      

   3. to make the setting affective execute, no reboot required

       $ sysctl -p
      

2. method 2

   1. use echo

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

   2. use sysctl

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

reference

1. https://www.unixmen.com/disable-ipv6-centos-7/