ifupdown with "inet6 dhcp" in /etc/network/interfaces breaks stateless
IPv6-conifg.

/etc/network/interfaces:
auto eth0
iface eth0 inet6 dhcp

auto configures eth0 with a ipv6-address but the networkdevice gets no gateway
from the radvd.

After that I bring the networkdevice down with "ifdown eth0" and then manual
with
ip link set dev eth0 up
or
ifconfig eth0 up
but the networkdevice don't get a gateway and or an ipv6-address (if radvd
advertise a addressprefix)

I have to reboot to solve the problem!

If I disable "iface eth0 inet6 dhcp" in /etc/network/interfaces reboot and do
it by hand:

ip link set dev eth0 up
        now the networkdevice has a gateway!
dhclient -6 eth0

everything ist fine.

/etc/network/interfaces
# statefull
iface eth0 inet6 dhcp

This will set /proc/sys/net/ipv6/conf/eth0/accept_ra to "0"
Now the client don't get a gateway address but dhcpv6 has no
option about router! I think setting the accept_ra to "0" is an error.

----- insert -----
Ok, i find out, that the accept_ra can be set with:
iface eth0 inet6 dhcp
	accept_ra 1
but the default ist "0". I think it is better to use "1" as the default,
because we need a gateway to work.
----- end insert ----



Another error: The timeout of the dhclient in ipv6-mode doesn't work. If
there is no dhcpv6-server ifup will hang. jessie + wheezy



If we use:
/etc/network/interfaces:
auto eth0
iface eth0 inet dhcp
iface eth0 inet6 dhcp

Then ifdown will use:
   ip link set dev eth0 down

for the ipv4-configuration an now ifdown fails to bring down eth0 for
ipv6. I think we need some testing before we switch the device down.

Hello,

It's not an error; if you want SLAAC + dhcpv6, you need to use auto,
not dhcp.

Hello,

Colin, could you please comment on this?