In the openstackdocstheme, one page should have a single title heading
(the highest level). If we have multiple title headings, only the first
one is shown at the top of the page and the remaining one(s) are not
shown in the main contents. (They are shown only in "Page Contents"
of the left TOC.) It is confusing a bit.
As far as I checked, this happens in two files in the current neutron doc.
It looks better to introduce a page title and keep the existing
titles as subsections.
There is no need to include a page on the L3 agent
as it is a separate page.