Currently the ipv6 external gateway is an admin configuration item. We want instead to have an API to set the ipv6 gateway.
Background:
The ipv6 router BP (https://blueprints.launchpad.net/neutron/+spec/ipv6-router) added a new L3 agent config called ipv6_gateway wherein an admin can configure the IPv6 LLA of the upstream physical router, so that the neutron virtual router has a default V6 gateway route to the upstream router.
This solution is however not scalable when there are multiple external routers per L3 agent.
Per review comments - https://review.openstack.org/#/c/156283/42/etc/l3_agent.ini
It is better to move this config to the CLI.
As discussed in the L3 weekly meeting - http://eavesdrop.openstack.org/meetings/neutron_l3/2015/neutron_l3.2015-06-11-15.04.log.html, this change aims to make this exact change by updating neutron net-create CLI will to now have a new option to set an ipv6_gateway (for the external router).
This is not an RFE, this is a normal bug. Removing the RFE tag.