Thanks, @Pierre-Yves, however, it doesn't seem to have made any difference.
Do you have anything special configured under the ethernet interfaces?
We just have the following -
iface eth0 inet manual
iface eth1 inet manual
I've configured the following ethernet bond [bond0], which appears to be working when both [eth0] and [eth1] are online, however, when I take down [eth1], IPv6 stops pinging for the node but not in the VMs. When I put [eth1] back online and take down [eth0], IPv6 is up for the node but...