fast.com has anycast nodes on most major ISP's so they can be misleading when there is a problem on your network. Have you verified the duplex/speed settings h

fast.com has anycast nodes on most major ISP's so they can be misleading when there is a problem on your network. Have you verified the duplex/speed settings have negotiated properly on each link of your LAN? What OS are you using? What is between your PC/phone and your Comcast modem? What make/model of NIC is on your computer?