Slow Network vmxnet gigabit?

Question

Hello friends,
I am having some speed issues regarding the LAN on a Windows XP Pro VM.
The Server is an i7, 16GB RAM, with SSD
The thing is extremely low speeds !! The Virtual NIC is bind'ed to a physical Gigabit.
I tested the speeds on the Server and 700 Mbits
I then tested speeds on the VM and:
TCP:
iperf -c server -t 60 -i 5 -w 2m
11.9 Mbits/s
UDP:
iperf -c server -t 60 -i 5 -u -b 1g
238 Mbits/s
I see that CPU utilization also goes up to 100%.
How can I find the problem?
Is it possible to change adapter from "vmxnet" to "e1000" on VMWare Server 2 ??

Answer 1

After fiddling around with the cabling and different configurations, I can confirm the problem actually lies with OpenSuse.
If I use iperf from a Live CD (grml) on the Laptop, both directions give full performance.
On the other hand, if I boot grml on the Desktop (replacing Arch) and the Laptop continues running OpenSuse, the problem remains.
What is even weirder is the fact that OpenSuse also manages to give full performance, if I have the cables connected before booting the system.
As soon as the system is running and I disconnect the connection for any time, the problem occurs again.
I suspect some form of duplex mismatch (http://en.wikipedia.org/wiki/Duplex_mismatch).
However, using ethtool, both systems agree that Auto-negotiation is on, the connection is full duplex and the speed should be 1000Mb/s (1000baseT/Full).
I guess I will simply ditch OpenSuse and install another Linux distribution on the Laptop.
Although I would like to understand the actual cause of the problem.