Setting the ARRIS wireless modem to Bridge/Router mode
By default, the modem is set to router mode. This means that the public IP (IP address assigned by the ISP) is taken by the modem. You will usually need to set your modem to Router Mode when your devices will be connecting to the Modem and no Routers will be involved.
To set your ARRIS modem to Router mode watch this short video:
This means that the modem will act as a bridge, i.e. the public IP (IP address assigned by the ISP) is going to be taken by the customer equipment such as the router instead of the modem.
To set up the modem to Bridged mode watch this short video: