Comment 10 for bug 1501969

It's certainly correct that the VM will not set up an SLAAC IPv6 address, if it does not receive any RA, or if its processing of RAs is disabled. So, if the RA is not reaching the VM, that is sufficient to explain what is being observed.

What is in the data path between the radvd and the VM? It should just be a matter of bisecting that path with tcpdump, to find out if the RA is being dropped somewhere.

Another possibility is whether the VM processes it. When my project was first testing IPv4, we needed a few tweaks in the guest (Ubuntu) OS:

    In /etc/network/interfaces.d/eth0.cfg, add:

    iface eth0 inet6 dhcp
            accept_ra 1

    In /sbin/dhclient-script, add at the start of the script:

    new_ip6_prefixlen=128

    In /etc/sysctl.d, create a file named 30-eth0-rs-delay.conf with contents:

    net.ipv6.conf.eth0.router_solicitation_delay = 10

(This is from http://docs.projectcalico.org/en/latest/ipv6.html.)

However, I can't immediately see why the presence or absence of any of those would make a difference between the VM processing an RA at boot time, and the VM processing an RA at some later time.

But maybe seeing this might trigger some thoughts?