Multiple parameters all to tune you kernel

List all tuning parameters

[root@centos7 ~]# sysctl -a | grep disable_ipv6
net.ipv6.conf.all.disable_ipv6 = 0
net.ipv6.conf.default.disable_ipv6 = 0
net.ipv6.conf.ens192.disable_ipv6 = 0
net.ipv6.conf.ens224.disable_ipv6 = 0
net.ipv6.conf.lo.disable_ipv6 = 0

Create a file /etc/sysctl.d/98-disable_ipv6.conf

[root@centos7 ~]# cat /etc/sysctl.d/98-disable_ipv6.conf
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1 

To disable in the running system:

[root@centos7 ~]# echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6
[root@centos7 ~]# echo 1 > /proc/sys/net/ipv6/conf/default/disable_ipv6

or

[root@centos7 ~]# sysctl -w net.ipv6.conf.all.disable_ipv6=1
[root@centos7 ~]# sysctl -w net.ipv6.conf.default.disable_ipv6=1