Laundry tub drain vent pipe

[greekguy7]

I have a laundry tub in the basement that tees into a drain and then goes thru the concrete floor. If you look upwards, it looks like the drain pipe also serves as a vent pipe too. Does that make sense? Anyway, several feet above where it tees in, there is a small hole in the vertical pipe which looks like intentionally done. I now noticed soap suds would ooze out of there and run down. The laundry tub drains fine. Any ideas? Should I plug the hole up? Sounds normal?

[Terry]

For every pipe that goes down (Waste line), there is one going up(Vent).
The vent should go through the roof.

That is normal.
The vent shouldn't have a hole drilled in it.