said by TheMayor:No I didn't. I just unplugged the original one & plugged in the replacement.
Graysonf is correct, I'm not getting the WAN IP address
Though not a cable user myself, I have helped two Comcast, and one Charter user with their cable modems and routers. As I recall, when changing the device attached to the cable modem Ethernet port, I had to reset, or power cycle the modem; and if it is a telephony modem, that includes disconnecting the battery.