Comment 5 for bug 1372317

If you check the "Disable Gateway" box you still need to enter a valid Gateway IP (or none) to move forward. If this box is checked and the field is hidden then the form should not care if the field is not valid. This issue doesn't seem to be fixed by either of the linked reviews above or this one either: https://review.openstack.org/211907. I hope this bug can be used to fix this.