If you can use something, it's useful. Useful things are handy for whatever you're doing. If something is just what you need or you just find it helpful, then it's useful. A hammer is useful in building many things. Coasters are useful if you don't want a coffee table to get stains. College degrees are useful â or necessary â for many careers.
Where is the security key on a comcast modem located? The security key on a Comcast Modem is located next to the serial  number of the unit. Sometimes the serial number is the number used  as a security code if it is not printeâ¦d on the device. (MORE) 1 person found this useful.
Your server or firewall (connected to the modem) should be configured with the following settings: 1  IP address: The IP addresses which can be assigned to equipment connected to the Comcast IP Gateway will be given to you once it is built. 2  Subnet mask: A CIDR /30 (or 1 static IP) - 255.255.255.252.