This is the Intel Atom 330 motherboard with integrated Realtek Gigabit NIC (Intel Desktop Board D945GCLF2 Motherboard W/ Atom 330 1.6 GHz Dual Core Processor - Mini-ITX)
I cannot achieve more than 15 MB/s, even doing a local transfer through eth0 to it's own IP.
100% 95MB 15.9MB/s 00:06
So this is not a cabling, switch or hardware issue, it seems like a driver or chipset limitation problem.
Here is my........