A number of bugs[1][2][3] have been filed which are related to updating the IPv6 attributes after a subnet has been created. In the reviews[4][5] for the fixes for [1] and [2] some shortcomings and questions have been raised, which were discussed in today's IPv6 IRC meeting[6]. Summary: In Juno we are not ready for allowing the IPv6 attributes on a subnet to be updated after the subnet is created, because: - The implementation for supporting updates is incomplete. - Perceived lack of usefulness, no good use cases known yet. - Allowing updates causes more complexity in the code. - Have not tested that radvd, dhcp, etc. behave OK after update. Therefore we are proposing to change 'allow_put' to False for the two IPv6 attributes, ipv6_ra_mode and ipv6_address_mode. This will prevent the modes from being updated via the PUT:subnets API. We would be interested to hear of any disagreements or questions. [1] https://launchpad.net/bugs/1362966 [2] https://launchpad.net/bugs/1363064 [3] https://launchpad.net/bugs/1373417 [4] https://review.openstack.org/125328 [5] https://review.openstack.org/117799 [6] http://eavesdrop.openstack.org/meetings/neutron_ipv6/2014/neutron_ipv6.2014-10-07-15.01.log.html