Comment 5 for bug 1953165

Brian: If my suspicion is right that this is a duplicate of that other bug, then this is not metadata specific. It is actually not even IPv6 specific, but only IPv6 has default DAD detection which detects that dhcp ports may leak traffic shortly while they are plugged to the dead vlan. This could be confirmed by having multiple v6 subnets with the exact same range, so neutron chooses the exact same address for the dhcp ports and this should go to dadfailed just as well as the metadata address does.

But regarding your metadata related question: only the dhcp namespace should have the metadata address configured. IIRC in the router namespace we do not have the metadata address configured. Instead we catch that traffic by an iptables redirect to the loopback address where haproxy listens.