The reasoning for a modem's four ports requires some explanation

Motorola MB8600 vs MB8611 The MB8600 model is designed for the future. Because it supports Ethernet port bonding for extremely high speeds or rates larger than 1Gbps, it should be linked with a router that likewise supports Ethernet port bonding for extremely high speeds or rates more than 1Gbps. These service tiers or routers are not now accessible, but will be in the near future. In the meantime, any router will suffice. The quantity of wireless technology available to you will be your discretion. An AC1900 wireless router would supply this. The Motorola MR1900 is a wireless router that supports AC1900.

The reasoning for a modem's four ports requires some explanation. It should be noted that the MB8600 does not support routing. The MB8600 is nothing more than a modem. A router can be connected to any of the MB8600's GigE ports. The connection between the router and the modem may then take use of the full rate of Comcast's new DOCSIS 3.1 service, which is currently one gigabit per second. In the future, Comcast and other cable companies are expected to introduce services that are faster than 1 Gbps. When such faster services become available, the additional ports on the MB8600 will be necessary. Ports 1 and 2 on the MB8600 may be linked together to provide up to 2 Gbps. The remaining two ports on the MB8600 are for additional port bonding at speeds more than 2 Gbps. When Comcast's service speeds surpass 1 Gbps, the router connected to the MB8600 must do port bonding as well in order to utilise the MB8600's port bonding. Consumer routers nowadays do not offer port bonding. Several routers used in commercial networks offer port bonding. Routers for homes and small businesses will be sold with port bonding capabilities in the future, allowing them to take advantage of future service rates greater than 1Gbps. In essence, the MB8600's four ports are there to let the MB8600 to provide service speeds greater than 1 Gbps WHEN THEY ARE AVAILABLE. That is a fantastic design. Think twice before purchasing a modem that claims to provide speeds more than 1Gbps but lacks several ports that can be connected. You won't be able to achieve a speed faster than 1 Gbps unless you have a technique to pull the fast speed out of the modem. The MB8600 is designed to provide up to 1 Gbps of bandwidth to a router with bonded GigE ports. Other modems are not as well made.

Multi-gigabit Ethernet speed — When enabled by your internet service provider, a 2.5 GB Ethernet port gives really high-speed access to even the most powerful routers and PCs, with downstream rates slightly less than 2,500 Mbps and upstream speeds of up to 800 Mbps. Gaming, conferencing, and fast streaming — Using Active Queue Management, it reduces Internet latency and increases app performance in areas such as online gaming, conferencing, and streaming (AQM). 5. Significant cost savings — Owning a modem saves the typical household $168 per year in rental fees. (Savings vary by service provider; Comcast Xfinity is used as an example.)