Bootstrap 3 - Fixed Responsive Navbar in container (without background color at the sides)

Bootstrap 3 - Fixed Responsive Navbar in container (without background
color at the sides)

How to?
Fixed navbar at center, but without background color at the sides.
The width of the navbar should be as that of the container and then the
background color of the navbar to the sides of the container (which
contains it) you should not see.
Any idea?
Furthermore the navbar must downsize at the resize of the width of the
container, and then of the page: so rensponsive navbar!
How to?
Thanks in advance.