Here are settings useful to maximize performance of a hardware network interface. Virtual guests benefit by these being applied to their virtual host, only. Not all of these exist on every NIC. There are also many settings which should not be touched, or should be touched only when the toucher knows what they are doing! The below have always helped when this writer has found them available to try. Do be warned, the NIC will go offline for 2-10 seconds after you Apply most of these.

1. Install the most current drivers for NICs and also motherboard chipset. In at least one case, the server vendor had only an outdated and unreliable driver available for download, the one which worked well for years came from Intel’s web site.
2. “DMA Coalescing” on.
3. “Enable PME” off.
4. “Energy Efficient Ethernet” off.
5. “Green Ethernet” off.
6. “Gigabit Lite” off.
7. “Adaptive Inter-Frame Spacing” on.
8. All offloading on.
9. “Interrupt Moderation” on.
10. “Interrupt Moderation Rate” should be “Adaptive”.
11. “Scaling”, should be “on” or “Enabled”.
12. “Receive Side Scaling” on.
13. “Receive Side Scaling Queues” to maximum.
14. There are cache settings on all server-class NICs, separate for send and receive. They are usually called “Receive Buffers” and “Transmit Buffers”, or “Receive Descriptors” and “Transmit Descriptors”. Set them to the maximum. For current Intel server NICs the defaults are usually 256 or 512, and the maximums are 2048; for a few other kinds, one or the other is 5000 or more; for others it is much less. Each descriptor takes 2K of RAM, which in today’s multigigabyte world is well worthwhile. Some older Broadcom gigabit NICs will yellow-flag if they are set to 2048; for these, set receive to 750, transmit to 1500.
15. In the NIC’s “Power Management” tab, turn everything off. This may have to be abridged if Wake-On-LAN is used. Some NICs, notably some Realtek, will automatically turn power management back on at boot; this needs to be fixed through group policy.
16. In SBS 2008, only one NIC (or one NIC team) is permitted to represent the server on the network. If there are two active NICs, you will have to turn one off, or crashes and unpredictable behavior will result sooner or later.