duplicated ipv6 prefix

Hello

When DHCPv6 is activated on an interface, I notice that radvd is started automatically to provide router advertisement with the managed flag, that's a good idea.

For each range a /64 prefix is advertised without the autonomous flag
but if I define several dhcp6 ranges inside the /64, the prefix is duplicated, it's a little bit strange !

For example, I use the DHCPv6 server and specify two ranges
[Range FC00::A000 through FC00::AFFF]
[Range FC00::F000 through FC00::FFFF]

In /etc/radvd.conf FC00::/64 is duplicated

prefix FC00:0:0:0:0:0:0:0/64
{
AdvOnLink on;
AdvAutonomous off;
AdvValidLifetime 2592000;
AdvPreferredLifetime 2592000;
};

prefix FC00:0:0:0:0:0:0:0/64
{
AdvOnLink on;
AdvAutonomous off;
AdvValidLifetime 2592000;
AdvPreferredLifetime 2592000;
};

In RA, the prefix is duplicated :

15:31:14.134935 IP6 (hlim 255, next-header ICMPv6 (58) payload length: 88) fe80::250:56ff:fea0:4440 > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 88
hop limit 64, Flags [managed], pref high, router lifetime 1800s, reachable time 0s, retrans time 0s
prefix info option (3), length 32 (4): fc00::/64, Flags [onlink], valid time 2592000s, pref. time 2592000s
0x0000: 4080 0027 8d00 0027 8d00 0000 0000 fc00
0x0010: 0000 0000 0000 0000 0000 0000 0000
prefix info option (3), length 32 (4): fc00::/64, Flags [onlink], valid time 2592000s, pref. time 2592000s
0x0000: 4080 0027 8d00 0027 8d00 0000 0000 fc00
0x0010: 0000 0000 0000 0000 0000 0000 0000
source link-address option (1), length 8 (1): 00:50:54:9e:00:ab
0x0000: 0050 569f 00ab