Why is iperf reporting < 400 Mbit/sec for a gigabit network?

I'm trying to test my network speed and I'm using iperf (because I don't know of any other tools) and I'm getting between 200 and 300 megabits per second every way I've tested.

Example:

Windows 7 to Router
Windows 7 to Windows Server 2008 R2
Windows Server 2008 R2 to Router

Hardware:

Windows 7 (Marvell NICs)
Windows Server 2008 R2 (Intel, dual-port, PCIe)
Router (Intel, on-board [Supermicro motherboard])
Switch: Netgear GS108T (managed switch, 8-port gigabit)

I can understand if the Marvell NIC in my Windows 7 machine is garbage but why am I only showing 200-300 between the server and router, both which have Intel chips?

Example from last my last run:

------------------------------------------------------------
Client connecting to 192.168.0.1, TCP port 5001
TCP window size: 8.00 KByte (default)
------------------------------------------------------------
[148] local 192.168.0.198 port 54279 connected with 192.168.0.1 port 5001
[ ID] Interval Transfer Bandwidth
[148] 0.0-10.2 sec 153 MBytes 126 Mbits/sec

Click to expand...

Is the router a supermicro atom 230/330 board? If so that would explain it because the onboard nics are shit on those boards.

jtg1993 said:

Is the router a supermicro atom 230/330 board? If so that would explain it because the onboard nics are shit on those boards.

Click to expand...

4. 2x Realtek RTL8111C-GR Gigabit LAN

Here's the board I have:

Supermicro X7SPA-HF-O

I've purchased it specifically for the Intel NICs...

What os on the router?

pfsense v1.2.3

It is a unresolved driver problem on freebsd 7.x (pfsense core os). If you really need that much speed across the router, choose a linux based distro with better drivers. I doubt the windows server machine has anything to do with this.

Crappy nics probably.

TCP window size: 8.00 KByte (default)

Click to expand...

Way too small. Try 100K or so.

Also get jperf.