I have been experiencing this for a long time. My speed is 15 download and 1 upload. I don't have a network card for my pc since im using wired connection. Whenever a pc or laptop connects to my modem or router the ping just starts to spike up and down non stop goes all the way up to 2000 sometimes. It mostly stays at 500-900. My modem can be a router at the same time, i also have a separate router but no matter which router pc's connects to the ping will always spike. I've tried to go to the modem and router website, everything i try won't work. I've reinstalled my realtek ethernet drivers, switched the wireless channels. The only options left is the dns relay for my router but the tickbox is locked for some reason and its always on no way for me to change it. My routers a d-link dir-615 and my modems a AR800 v2.5. Also ping only spikes when pc/laptops connects to the internet, never spikes when my friends and i connect our phones to the router/modem.