ok, so yesterday i wire 75 foot cable from RT-AC66U to DIR-655. then it will not work, link isnt happening, so i take the same cord, plug into modem instead of RT-AC66U, link works. hmmmmm change cable to RT-AC66U link works. shows up at 10mbps. but doesnt work, cant ping the router, then using same 2 cables, i went RT-AC66U ---> Swtich ---> DIR-655 and it worked. the RT-AC66U created the problem. the switch solved it. i dont wanna have to use a pointless switch!