WinDbg, host machine lose network if test machine is on the same switch

Question

I have a really strange problem with WinDbg and would like to know if anyone can explain to me why it happens.

So here is the setup:

• Debugging a target Windows 7 64bit machine with WinDbg
• Host machine running Windows 7 64bit also
• Host and Test machines connected via firewire
• Host and Test machines connected to the same switch (a Netgear gigabit switch, 8 port)
• Break into the test machine

Problem: After about 10 seconds the host machine loses network connection

What resolves the problem immediately:

• Run on test machine (Go)
• Unplugging the test machine's Ethernet cable

Does anyone know why this happens, and if there are solutions?

Curculio

Answer 1

Try disabling Flow Control on the network adapter of your target machine (generally there is an option in the Device Manager settings for the device). If you don't have a specific flow control option (or even if you do), also set the network adapter to Half Duplex mode.

Sheenasheeny

When the target is stopped, the driver for the NIC is also stopped. However, the NIC still keeps on running and receiving network data. At some point the buffers on the NIC fill and it sends a pause frame, which can cause the switch to stop sending traffic to all ports (not just the affected one). – Sheenasheeny