We have multiple Ethernet cables from around the house plugged into the router, I found that my ping (used ping www.google.com -t) is 100% perfect when the ethernet cord from my brothers room isnt plugged in. As soon as that cable is plugged into the router, I get ping spikes every 10 or so seconds. The Ethernet cable causing the issue doesn't even need to be plugged into a computer to cause it. All the cables are a week old and are identical models. Also, this doesn't happen when other ethernet cables from other sources are plugged in, its just that specific one. Is there a reason for this?