How to enable ipv6 temporary addresses and make them preferred for outgoing connections in CentOS

Enter these two command from a root shell:
sysctl net.ipv6.conf.all.use_tempaddr=2
sysctl net.ipv6.conf.default.use_tempaddr=2
To make them permanent add these two lines in /etc/sysctl.conf
net.ipv6.conf.all.use_tempaddr=2
net.ipv6.conf.default.use_tempaddr=2
After that restart network service:
service network restart