Virtnet, Configuring and Customizations

Virtnet is a really cool little tool, thats been a lot of fun messing around with. Windows drivers not being one of my strong suites. In the Topic Using the virtual network adapter VirtNet ➡ , Post #6, hinted at a way to set the default Mac. So I started messing around to see what I could do.

‘Out of the box’ Virtnet’s MAC is 02-00-4C-4F-4F-50, and this Hex string can be seen occurring only once in the driver file Virtnet.sys, starting at &H84C. However changing the value, renders a driver code 39 “Driver corrupt or missing”. I’m guessing it has some sort of check sum.

The I switched gears over to the .inf file, which has some commented sections on making changes.

[ControlFlags]

// Note: Uncomment next line if your NIC is not to be installed manually

;ExcludeFromSelect = *NM_VIRTNET 	

[Models]

; Note 1. Replace the bogus *NM_VIRTNET  "hw-id" with a real hardware PnP ID

; Note 2. Optionally, add more NIC models supported by this file

;

; DisplayName        Section           hw-id

;





%*VIRTNET.devicedesc%=*virtnet.ndi, *NM_VIRTNET  

;

; Optional Custom Parameters in the Registry ("Advanced" menu).

[VIRTNET.params.reg]

; For example:

HKR, NDIparamsNetworkAddress,           ParamDesc,      0, %NetworkAddress%

HKR, NDIparamsNetworkAddress,           type,           0, "edit"

HKR, NDIparamsNetworkAddress,           LimitText,      0, "12"

HKR, NDIparamsNetworkAddress,           UpperCase,      0, "1"

HKR, NDIparamsNetworkAddress,           default,        0, " "

HKR, NDIparamsNetworkAddress,           optional,       0, "1"

The third Section, in key “NetworkAddress” called Default seemed really interesting. However, as far as I can tell on XPsp2 it does nothing when set to a MAC. The Rom/Hard MAC is still 02-00-4C-4F-4F-50, and the soft MAC is still unset, with no value.

I did get a driver installed MAC to work by Setting the Soft MAC by adding the following to a reg section of the inf.

HR, , NetworkAddress, 0, "00CCCCCCCCCC"

This simply replicates the driver setting a Soft MAC in the windows registry, and isn’t really changing the default MAC. It has left me wondering what these settings do. Could we possibly get a rundown on the function of these settings? And can we get a description of how to Change the Default MAC that Topic Using the virtual network adapter VirtNet ➡ , Post #6, hinted at? If there have been Previous Posts, or some documentation that I simply missed, just point me in the right direction.

As a side note, Is there a checksum in windows driver files?