I created a Centos 7 LXC container. I assigned IPv4 and IPv6 space to it. IPv6 did not work. Looking at container it added the IPv4 address too /etc/sysconfig/network-scripts/ifcfg-eth0 and added IPv6 address too /etc/sysconfig/network-scripts/ifcfg-eth0:0. Moving the IPv6 address too ifcfg-eth0 allowed it to work. Any idea what would be causing that? It does not appear to be picking up any of the settings in :0 file.