It is not a unified response from all my machines; only a small minority of machines are doing this (2 of 10 at the moment).

I'm going to make certain the ports are active in my server room but I've already switched a known working Apple machine's Ethernet with one that is returning the three slashes and received the same results.

Of the two machines the MacBook Pro laptop was able to get it properly after a couple retries but the iMac desktop still showed the three slashes after every retry. I have yet to re-test the devices (and get back with my results).