It's important to remember that the MB8600 lacks

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The reasoning for a modem's four ports has to be explained. It's important to remember that the MB8600 lacks routing capabilities. The MB8600 is nothing more than a modem. A router can be connected to any of the MB8600's GigE ports. The full rate of Comcast's new DOCSIS 3.1 service, which is currently one gigabit per second, may then be used between the router and the modem. In the future, Comcast and other cable companies are expected to provide speeds faster than 1 Gbps. The MB8600's additional ports will be necessary when such faster services become available. The MB8600's ports 1 and 2 may be combined to provide up to 2 Gbps of bandwidth. The additional two ports on the MB8600 are for extra port bonding for speeds more than 2 Gbps. To take use of the MB8600's port bonding, the router connected to the MB8600 must likewise execute port bonding when Comcast's service rates surpass 1 Gbps. Consumer routers nowadays do not offer port bonding. Several routers used in commercial networks offer port bonding. Household and small-business routers will be sold with port bonding capabilities in the future, allowing them to take advantage of future service rates greater than 1Gbps. The four ports on the MB8600 are essentially there to allow the MB8600 to provide service rates greater than 1 Gbps WHEN THEY ARE AVAILABLE. That is a fantastic design. Consider carefully before purchasing a modem that claims to provide speeds more than 1Gbps but lacks several ports that can be joined. You won't be able to acquire a speed higher than 1 Gbps unless you have a way 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 aren't as well constructed.

Update...... BestBuy has one, and YES, you can use both ports at the same time. My PC is linked to the 2.5 port, and my Asus Ax11000 router is connected to the other port. I hope you find this information helpful. The Arris S33 is a 32 × 8 DOCIS 3.1 device with up to 2.5 Gb speeds. While the modem is on the Xfinity acceptable equipment list (for more information, visit dslreports.com), it is your router that is important. Make sure your router can handle at least 1 gigabit per second of traffic. 8 upstream x 32 downstream 2 downstream x 2 upstream DOCSIS 3.0 bonded channels DOCSIS 3 1 OFDM channels For blazing-fast internet, connects to any existing Wi-Fi network. Compatible with major cable Internet providers in the United States, including as Cox, Spectrum, Xfinity, and others. ice.

Spend Less – Rental rates for cable modems might be reduced by up to 168 dollars each year (Savings are shown for Comcast Xfinity and vary by cable service provider.) Comcast Xfinity and Xfinity X1, Cox, and CableOne have all approved it for all speeds, including Comcast Gigabit and Cox Gigablast. RCN is incompatible with this. Fiber optic, DSL, and satellite services from Verizon, AT&T, CenturyLink, Frontier, and others are not compatible with cable modems.) Flexible Compatibility – Works with any Wi-Fi router, including Whole Home Wi-Fi and Mesh routers such as eero, Google Wi-Fi, and Orbi. Any SINGLE equipment with an Ethernet port, such as a router, Windows or Mac computer, HDTV, or gaming station, may be connected to a 10/100/1000 Gigabit Ethernet port. This cable modem does not include a built-in wireless router or the capacity to make phone calls.