House with FTTP but only one ethernet port next to NBN box

Hi everyone, i've been combing through all the posts relating to this problem but I just can't find how to work around it... Here it goes.

I have a NBN box in the garage and underneath it there is one ethernet port. So far, I have been connecting the internet router directly to the NBN box uni-D1 port and using wireless at home. Then one day I realised with the fttp at home I should be able to connect the ethernet port from the garage to another point in the house (hopefully in the living room). I tried all the ethernet ports and none of them seems to work.

What's weird is there's only 1 ethernet port in the garage under the NBN box but there's 6 ethernet ports in the living room. It makes me think that the 6 ethernet ports connect to the rooms around the house. If that's the case, how do I connect NBN box from the garage to the living room, if the one ethernet port in the garage doesn't seem to connect to any of the ports in the living room?

I feel like I'm missing something here..... Would appreciate any input. Thanks in advance