Comment 9 for bug 1629133

Let me provide some context: I think this stems from patches [1,2]. Perhaps we can strike a balance between my overly conservative and Assaf's overly aggressive range. I intentionally chose different defaults from FIXED_RANGE_* because I felt the two were not quite the same as pointed out in comment #1. For this reason, I am slightly reluctant to embrace fix [3], even if it does the trick.

Ultimately these values can be overridden at user's leisure, and we can ultimately choose sensible defaults in devstack-gate if need be. Bear in mind, there is some documentation available in [4].

[1] https://review.openstack.org/#/c/282559
[2] https://review.openstack.org/#/c/283289
[3] https://review.openstack.org/#/c/379543
[4] http://docs.openstack.org/draft/networking-guide/config-subnet-pools.html