Title. I've my PC and my Steam Link connected to my TD-W9980, both with a Cat6 cable (I got multiple from work). Cable is working I swapped it and tested both old and new. Do I have to put some exception inside my router firewall to better allow these two devices to see each-other?
On the “minor request”, those first two allow things like SIP and microcells, along with encrypted services, such as from cell phones, to work (“IPSec”). Yes, the third is so you can get an IP from your ISP.