J'ai passé dhcp6c en mode débug et voilà ce qu'il me donne
Apr 29 08:19:05 dhcp6c 9813 freeing op data at 0x800e1f080
Apr 29 08:19:05 dhcp6c 9813 freeing op data at 0x800e28370
Apr 29 08:19:05 dhcp6c 9813 reset a timer on igb0.832, state=REQUEST, timeo=0, retrans=909
Apr 29 08:19:06 dhcp6c 9813 receive reply from fe80::ba0:bab%igb0.832 on igb0.832
Apr 29 08:19:06 dhcp6c 9813 get DHCP option IA_PD, len 41
Apr 29 08:19:06 dhcp6c 9813 IA_PD: ID=0, T1=88767, T2=207360
Apr 29 08:19:06 dhcp6c 9813 get DHCP option IA_PD prefix, len 25
Apr 29 08:19:06 dhcp6c 9813 IA_PD prefix: 2a01:cb14:8288:7d00::/56 pltime=259200 vltime=259200
Apr 29 08:19:06 dhcp6c 9813 get DHCP option server ID, len 20
Apr 29 08:19:06 dhcp6c 9813 DUID: 00:02:00:00:05:58:44:45:53:48:41:59:45:53:53:55:44:52:4f:54
Apr 29 08:19:06 dhcp6c 9813 get DHCP option client ID, len 14
Apr 29 08:19:06 dhcp6c 9813 DUID: 00:01:00:01:25:dc:54:c1:40:62:31:03:dc:58
Apr 29 08:19:06 dhcp6c 9813 get DHCP option authentication, len 27
Apr 29 08:19:06 dhcp6c 9813 proto: unknown(0), alg: unknown(0), RDM: mono counter, RD: 0000 0000 0000 0000
Apr 29 08:19:06 dhcp6c 9813 Discarding null authentication
Apr 29 08:19:06 dhcp6c 9813 dhcp6c Received REQUEST
Apr 29 08:19:06 dhcp6c 9813 make an IA: PD-0
Apr 29 08:19:06 dhcp6c 9813 create a prefix 2a01:cb14:8288:7d00::/56 pltime=140733193647232, vltime=34359997568
Apr 29 08:19:06 dhcp6c 9813 skip igb0.832 as a prefix interface
Apr 29 08:19:06 dhcp6c 9813 executes /var/etc/dhcp6c_wan_script.sh
Edit: en virant l'option 6 rien ne change
Si je vais dans mes interface je constate deux même adresses: