Octavia uses an ipv4 subnet (/16) for its management network.
When dealing with Edge deployments, it needs additional subnets (networks) with similar parameters (/16), so it requires the pre-allocation of a lot of routable IP addresses and it may be complicated to find an unused /16 private range.

To mitigate this issue, Octavia should be able to use a private ipv6 subnet for the management network. This ipv6 management network would not be enabled by default, but an option in Tripleo would enable it.

Additional considerations:
- need to think about the update from an ipv4 to an ipv6 management network
- need to add a CI job with this option