macosx: how to reload ethernet kext?

Question

I was thinking about a kextunload followed by a kextload but that didn't really worked:

%sudo kextunload /System/Library/Extensions/IONetworkingFamily.kext/Contents/PlugIns/AppleYukon2.kext 
(kernel) Can't unload kext com.apple.iokit.AppleYukon2; classes have instances:
(kernel)     Kext com.apple.iokit.AppleYukon2 class sk98osx_dnet has 1 instance.
(kernel)     Kext com.apple.iokit.AppleYukon2 class yukon has 1 instance.
(kernel)     Kext com.apple.iokit.AppleYukon2 class yukon2osx has 1 instance.
Failed to unload com.apple.iokit.AppleYukon2 - (libkern/kext) kext is in use or retained (cannot unload).

%sudo kextload /System/Library/Extensions/IONetworkingFamily.kext/Contents/PlugIns/AppleYukon2.kext

After that, I am getting this:

%ifconfig en0
ifconfig: interface en0 does not exist

Each further try with kext(un)load doesn't change anything in that situation.

While trying that, I am getting these messages in kernel.log:

Nov  1 02:05:17 76-128 kernel[0]: Can't unload kext com.apple.iokit.AppleYukon2; classes have instances:
Nov  1 02:05:17 76-128 kernel[0]: Kext com.apple.iokit.AppleYukon2 class sk98osx_dnet has 1 instance.
Nov  1 02:05:17 76-128 kernel[0]: Kext com.apple.iokit.AppleYukon2 class yukon has 1 instance.
Nov  1 02:05:17 76-128 kernel[0]: Kext com.apple.iokit.AppleYukon2 class yukon2osx has 1 instance.
Nov  1 02:06:32 76-128 kernel[0]: AppleYukon2: 00000000,00000000 sk98osx_dnet - AllocIOInterruptHandler - Failed to allocate MSI interrupt
Nov  1 02:06:32 76-128 kernel[0]: AppleYukon2: RxRingSize <= 1024, TxRingSize 256, RX_MAX_LE 1024, TX_MAX_LE 768, ST_MAX_LE 3328