I have 2 gigabit eathernet connections (nVidia motherboard), and I would "team" them, so they work together. I did this in Windows using the nVidia control panel.
NVIDIA DualNet technology
The NVIDIA DualNet® technology brings a number of advanced enterprise-level network technologies to the enthusiast, including teaming and TCP/IP acceleration. Teaming doubles the network link by combining the two integrated Gigabit Ethernet ports into a single 2-Gigabit Ethernet connection to increase the overall link speed with high availability and redundancy. TCP/IP acceleration reduces CPU utilization by offloading CPU-intensive packet processing tasks to hardware, using a dedicated processor for accelerating traffic processing plus hardware-optimized software.
Ubuntu Hardy Heron 8.04 user/ Vista Dual Booter