Yes, it's in one monolithic file.
Try making a minor typo in the syntax, then restart networking. You will lose all network connectivity on ALL interfaces.
Fix your typo and try to start networking again. It won't work until you reboot.
Or you can try adding your config to one of the seemingly infinite network config subdirectories (ifup.d, post-ifup.d, etc). Make the same typo anywhere in the subdirectories and you'll still mess up all networking and have to reboot.
I guess this is acceptable if you haven't used any OS besides Windows 98. For the rest of us it's maddening.
Shuttleworth has done nothing but help the open source community in every way imaginable.
You really consider a distro that can't change basic network configuration without a reboot to be 'helping'? Worse yet, some insane people are even using it as a server OS.
I hear there are only crap informercial for closetted ghery asstards on that silly excuse for a web site. Even Taco had some more to offer instead of that junk.