I am going to agree to SOME extent with Doc E on this one. While I don't necessarilythink dogs "need" to be contained, it sure does help in many ways. For one, you can put the dog somewhere they can call "home" that is safe when you are not around. You also avoid dogs digging in the nice part of your yard, and when you leave, you can put the dog in the kennel. It also teaches them to be more content when you put them in small places outside of home. All you need is about a 10 foot by 5 foot kennel with a doghouse. You can put it down the side of your house or somewhere in the shade, and even cover it if you want for a good place on those rainy nights you have compandy and don't want the dog tracking in mud.
Now, I don't think a dog needs this to be a well-behaved dog, but it can really help you progress and give your dog a secure place.

By the way, some dogs go through a stage at this age when they are rascals. You have to stay on them gently but firmly and before long, you'll have a good old buddy.