Ethernet Link Aggregation
For a heavily used Mac Pro server, network bandwidth can be a bottleneck. Fortunately, the operating system gives you an inexpensive way to more than double your Ethernet bandwidth.
Link aggregation combines two or more Ethernet ports to enable them to work as one port. The bandwidth of the aggregated port is the sum of all the ports, so aggregating two 1-gigabit Ethernet ports gives you a 2-gigabit port. Before you aggregate the Mac ports, you need to set up link aggregation on your Ethernet switch. How you do this depends on the switch you are using.
But on the Mac, OS X lets you aggregate ports in the Network pane of System Preferences. Click the Action (gear) icon at the bottom of the pane and then select Manage Virtual Interfaces to display a screen of the same name. Click the Add (+) button and then select New Link Aggregate. In the dialog that appears, enter a name for the aggregated link and select the check boxes for the Ethernet ports that you want to include in the aggregate. Finally, click the Create button. Your new aggregate appears in the dialog.