ANSWER: The MB8600 is a cable modem bridge that normally only connects to one device, such as a router, computer, HDTV, game station, or other device. We built the product with four Ethernet ports ONLY for two situations that don't apply to most customers, namely Port Bonding and Multiple Assigned IP addresses:
1. LAG Support for Port Bonding
The MB8600 hardware offers LAG support when connected to devices that implement LAG. LAG stands for Link Aggregation Group. Devices that support LAG can bond two or more Ethernet ports together, and achieve higher throughput speeds.
For the vast majority of customers, a single Gigabit Ethernet connection will provide ample throughput. As of this writing, the highest DOCSIS cable speeds offered are one gigabit per second. When higher DOCSIS speeds are offered in the future, LAG support will be required to take advantage of those speeds.
As of this writing, there are no consumer level routers or PCs that support LAG. Commercial network equipment is available that does support LAG. We plan to evolve the MB8600 firmware so that first it supports bonding of two ports, and later supports bonding of four ports. If you need to know how much bonding is supported on a given date, please contact Motorola customer support.
2. Cable Internet accounts with multiple assigned IP Addresses
The vast majority of residential accounts have only one assigned WAN IP Address. In these cases, the modem passes through that one IP Address. If you have a standard residential account with your cable provider, you can connect a router to one Ethernet port on this modem to allow internet access to multiple devices.
If your account with your cable provider includes more than one WAN IP Address, then the other ports on this modem can pass through up to three additional IP Addresses. In that case, you can connect devices to up to all four of the MB8600’s Ethernet ports.
If you want to use the MB8600 for either of these two situations, you simply remove the tape that covers those ports. Instructions HERE