[CentOS] Help with IPv6 /48 block

Hello.

It happens that at the company I'm working decided to start migration of 
IPs tech.

So they got a /48 block. I were trying to add it with:

ifcfg-eth0-range1 (0 is already in use with IPv4 range):

IPV6ADDR_START=xxxx
IPV6ADDR_END=xxxx
CLONENUM_START=0

But of course I am assuming that like in IPv4 IPADDR_START/END is 
implemented.

Please give some guidance as I need this to done already and the hole 
/48 must be available and virtualized.


Thanks.