Comment 9 for bug 1888256

Hi,

I was looking into that issue today. And when I was trying to reproduce this locally, I created network, then subnet with same setting as Yours and then I tried to attach this subnet to the neutron router and I got error like:

(overcloud) [stack@undercloud-0 ~]$ neutron router-interface-add test-router 3982beee-c13f-4e51-beca-60b82405d34a
neutron CLI is deprecated and will be removed in the future. Use openstack CLI instead.
Bad router request: IPv6 subnet 3982beee-c13f-4e51-beca-60b82405d34a configured to receive RAs from an external router cannot be added to Neutron Router..
Neutron server returns request_ids: ['req-af19e405-49d9-4efd-ad78-dd033dab9532']

But when I created port in this network and added it to the router then it worked without error.
So IMHO this sounds like it shouldn't be supported by Neutron at all to plug such subnet to the Neutron router but we have bug in the validation when we are plugging port to the router.

This validation is in neutron since https://review.opendev.org/#/c/136733/ which was merged many years ago.

I opened separate bug for that validation issue https://bugs.launchpad.net/neutron/+bug/1889619 and I will propose patch to fix it so Neutron will not allow to plug such port to the router anymore.