In newer 7.x versions there is a really rudimentary support available, see /etc/rc.config for details.
Because of the really different configuration and script file structure it is hard (or impossible) to use the set for Red Hat Linux and clones with this distribution. In versions 8.x they completly change their configuration setup.
Edit file /etc/sysconfig/network/ifcfg-<Interface-Name> and setup following value
IP6ADDR="<ipv6-address>/<prefix>"