For some reason I won't get an IPv6 address when rebooting my Debian 8 System, while I get one when restarting the networking service. The DHCPv6 server is up and running (and is answering when using dhclient or restarting the networking service).
/etc/network/interfaces:
auto lo
iface lo inet loopback
iface lo inet6 loopback
allow-hotplug eth0
iface eth0 inet6 dhcp
iface eth0 inet dhcp
What do I have to configure to get an address when booting?