I have inherited an NDIS 5.1 intermediate driver which runs correctly under XP yet with Vista the processor occupancy shoots up as soon as the user part of the application (a firewall) is started. The culprit appears to be the time taken to call the Windows GetIfTable function. A simple test app shows that a call to this function prior to installing the driver takes around 3ms yet this increases to 220ms once the driver is installed.

Neither static analysis (PREfast and SDV) nor dynamic testing (verifier) highlighted any issues with the driver.

I’m using the latest WDK and building the driver in the XP checked build environment.

Any suggestions as to possible issues with the driver or information as to how GetIfTable interacts with driver are gratefully received.

Thanks for your time

Dave