Comment 3 for bug 1888256

Sorry for the slow response.

I have more questions as I'm trying to understand the use case.

1) You have a shared provider network, but instead of being external it's internal.

2) You allocated public v4/v6 addresses to instances on it, so don't require NAT.

3) What purpose does the neutron router perform? Is it routing between subnets on this network, or multiple shared internal networks? It almost doesn't seem like you need the neutron router.

When I tried to recreate this using a subnet I created with ra-mode=None/address-mode=slaac, and then adding an interface to a router I get:

Error: Failed to add interface: Bad router request: IPv6 subnet 6c7c4a89-15fd-4627-b30f-92f306c8e11f configured to receive RAs from an external router cannot be added to Neutron Router.. Neutron server returns request_ids: ['req-ef172dc4-b5ea-4edc-84f1-53173287b4bc']

I could successfully add interfaces for IPv6 subnets with None/None for the modes, and I don't see radvd advertising a prefix, so I'm not sure how you did this yet.