Or two small, co-located companies may be sharing resources.

For example, one might be a production and the other an experimental network (or a back up). However, it may happen that a home or, more often, a small business may have two separate networks. Those scenarios are generally reflected in the top half of Figure #1 shown below, using just one Ethernet port on a Mac Pro.

Cable Modem > Wireless Router with ports > Macs, iPads etc.

Cable Modem > Router > Switch > AirPort, Macs, iPads, etc.

If course, at home, some typical configurations are: That's a situation that doesn't usually arise in a home, but it could. What I'm going to discuss here is a connection to two networks, simultaneously. Other configurations include, for example, something called 'link aggregation.' That's when two Ethernet ports are combined to achieve greater bandwidth. This article is focused on the ones I'm familiar with and have tested. There are several reasons why one might want to utilize both of these Ethernet ports. How and when would one want to use both of these ports? I'll discuss a pair of typical scenarios.

Unlike all other Macs, the Mac Pro line has two Ethernet ports.

Ethernet adapter for mac pro