There was a strange thing I noticed when I moved from the rented router/modem combo provided by Comcast to a netgear Cm1000. The speed rate average dropped from

There was a strange thing I noticed when I moved from the rented router/modem combo provided by Comcast to a netgear Cm1000. The speed rate average dropped from 700mbps to 2-300mbps. Is this a configuration problem?