I had the same experience. I have comcast and I bought a Motorola SB6121 on amazon because it was $85 and comcast charges you $7/mo to rent a cablemodem so you

I had the same experience. I have comcast and I bought a Motorola SB6121 on amazon because it was $85 and comcast charges you $7/mo to rent a cablemodem so you save money after only one year. Anyway, I plugged the modem in, it downloaded some config, rebooted, and started talking to comcast. It was pretty painless. And I just picked the cheapest docsis 3 modem off a list of probably 25 approved models.