Good day

Please Help, I want to know what are the core things a 3rd year undergraduate student should know in NETWORKING and TECHNICAL SUPPORT in other to be practically competent, so that they won t struggle when the start working in real life because most schools tends to focus more on theory or waste time on unnecessary practical’s instead of giving student the real deal.

I think you are getting the real deal. Every job situation is different, so theory and 'practicals' pretty much cover everything.
This is a strange question. 'Core things a 3rd year' student should know sounds like a homework question.
You are expected to tell us if it is homework, and to try to answer it yourself first.
Is it?

If you get a job in technical support, you learn the products they start you on, inside and out. You take notes and get used to their online technical help. You mainly learn how to soothe the frustrations of a lot of people who yell at you on the phone or chat. Not the most pleasant job, but a good starter one. What else is there to say?

The core thing you need to know is follow the bosses instructions.