If you mean did I power cycle the modem, yes, several times and often. It's just a dumb modem with no routing capabilities at all. Motorola SB6141.Was the C7 attached to the cable modem wan port before the server? If so, did you release the C7 dhcp lease before plugging in the server to the cable modem?
When I've switched routers on Comcast, the new router would not immediately obtain a new IP address until I released the dhcp lease on the old router or until the lease on the old router expired.