[clug] IPv6 config on Jessie not working

[Bob Edwards]

Giving up trying the mess that is Google searching and going for the
tried and true widsom of the CLUG list!

I have a server with multiple interfaces, some with both IPv4 and IPv6,
running Debian Jessie.

My /etc/network/interfaces file has many stanzas, but includes
something like:

auto eth0.1119
iface eth0.1119 inet6 static
         address a:b:c:f::g
         netmask 64
         up echo 1 > /proc/sys/net/ipv6/conf/eth0.1119/forwarding

# The primary network interface
auto eth1
iface eth1 inet static
         address w.x.y.z
         netmask 255.255.255.0
         network w.x.y.0
         broadcast w.x.y.255
         gateway w.x.y.1
         up /etc/network/rc.firewall

iface eth1 inet6 static
         address a:b:c:d::e
         netmask 64
         gateway a:b:c:d::1
         up echo 1 > /proc/sys/net/ipv6/conf/eth1/forwarding

(note that eth0.1119 does not have an IPv4/inet stanza, ie. the IPv6/
inet6 stanza is the only one for that interface).

The interfaces with only an IPv6 stanza (such as eth0.1119) come up
correctly with an IPv6 address at system boot, and the IPv4/inet
address is assigned correctly for eth1, but no IPv6/inet6 address is
assigned for eth1.

There is another interface with two stanzas, first one for IPv4 and
second for IPv6, and the IPv6 address is not being assigned for that 
interface either.

This all used to work correctly, but seems to have stopped, maybe
as long ago as the upgrade from Wheezy to Jessie (I think I may have
manually set the IPv6 addresses some time ago and not got back to
investigating why it wasn't set automatically).

Anyone got any clues/suggestions as to what I am doing wrong here?
Any ideas how I can enable some logging to see if the system might
want to tell me why it isn't assigning the IPv6 address?

cheers,

Bob Edwards.