I have been using dhclient for getting ipv6 address on linux centOS clients.
It was all working fine till centOS6 untill i migrated to centOS7+dhlcient-4.2.5.
I see /proc/net/if_inet6 file.
[root@fazorboy ~]# cat /proc/net/if_inet6
fe800000000000000xxxxxxxxxxxxxxx 02 40 20 a0 eth0
00000000000000000000000000000001 01 80 10 80 lo
10240000000000000xxxxxxxxxxxxxxx 02 40 00 00 eth0
20010718080200000xxxxxxxxxxxxxxx 02 40 00 00 eth0
2001071808020000xxxxxxxxxxxxxxxx 02 40 00 00 eth0
Fifth column should be 80 for permanent address and its 00 for cent7. but for cent6 it shows 80.
dhcp server is not changed and same is service for centos6 clients working fine.
its possible that something has changed either in dhclient or cent7 making same dhclient request behave differently.
please let e know if need more information?