[CentOS] Centos 7 Server Forgets IPv6 Address On Reboot

My Centos 7 server has started to forget its IPv6 address on a reboot.
This causes problems with services being unable to start up.

It's easy enough to fix each time (ip addr add ...), but it would be
nice to be able to convince it to retain that information. Presumably,
there's a file somewhere under /etc/sysconfig that should contain this
information - does anyone know where it should be stored?

Thanks,

Dave...

-- 
Dave Cross :: dave at dave.org.uk
http://dave.org.uk/
@davorg