Do they know its an ivy?

Is this a trick question? Of course they know! Why would you think otherwise?

In Penn they do, and a few other places, but in general not really and it will also depend on the degrees you got from there,

Also except in some issues, the actual university makes little difference as to the fact you have a university degree. Also, if you graduated form same school as the HR or Owner went to, even if it was a minor small school, it may men more.

I didn't know it was Ivy League until just now, when I looked it up.

It doesn't have the cachet it had years ago. Now employers want to see how well you did and what your areas of concentration were, and unique accomplishments while there. But even that is only a precursor to a good interview.