I installed Ubuntu 14.04 server a week ago. I use it as a virtual machine host (tasksel installed). meaning am running it with kvm + libvirt.
I have set up the same bridge I had in 13.10.
auto p4p1 iface p4p1 inet manual up ifconfig $IFACE up down ifconfig $IFACE down auto br0 iface br0 inet static address 46.182.xxx.xxx netmask 255.255.255.240 gateway 46.182.xxx.xxx dns-nameservers 46.182.xxx.xxx 46.182.xxx.xxx bridge_ports p4p1 bridge_stp off bridge_maxwait 0 iface br0 inet6 auto
Against br0 I connect my virtual machines with
<source bridge='br0'/> defined in libvirt.
My virtual machines get Router Advertisement messages without problem. All virtual machines get IPv6 addresses.
My problem is that IPv6 does not work over the bridge. But it does work when I turn on tcpdump against br0 for troubleshooting. I have tried setting the interface manually into promiscous mode but that does not make it work,
ifconfig br0 promisc.
Why I have the IPv4 addresses on the bridge? I do not know, old habit, never question it. IPv6 does not work on the virtual machine host but the host get IPv6 address by RA, just like the virtual machines.