If it really is becoming obscure that's a shame, I'm not sure how you could pretend to understand how IP networks work without having at least cursory familiarity with it.
If I was hiring a network technician, I definitely wouldnt hire someone who didn't know what ARP is. It's too easy and fundamental to the field. It took all of like 3 weeks at the trade school I attended to cover IPv4, MAC, ARP, basic routing protocols, TCP, and UDP, and we were definitely chilling. Understanding those things isn't complicated. You just need to know what computers are, and what "networks" are, then it all very easily clicks into place.
I had a job interview today and they asked me to describe TCP and udp, and when I did they told me not everyone knows it nowadays. I guess I can see why, if you're a web dev you never have to worry about such things.
