Guy Harris

> `The system cannot find the device specified. (20)).` Error 20 is `ERROR_BAD_UNIT`. [OSR's handy table of NT status to Windows error code mappings](https://www.osr.com/wp-content/uploads/NTtoDos.pdf) doesn't show any NT status that...

> One potential suggestion: the original network adapters may be able to be opened for capture, even if they don't show up in Wireshark's listing. That matters only in the...

> windows server 20212r2 ... > On current Windows server 2012r2 Is that Windows Server 2012 R2, which hasn't been the current version for a long time, or is that...

So that's "Windows 8.1 Server", at least according to [the Wikipedia article](https://en.wikipedia.org/wiki/Windows_Server_2012_R2), so it should still be supported. (Perhaps the Npcap home page should say something such as "Npcap works...

> Winpcap on the contrary finds the physical interfaces, but not the loopback one. WinPcap doesn't show the loopback interface because the loopback interface is an Npcap-implemented device. > So...

See also nmap/npcap#72.

> I was getting that error when trying some commands from > > https://npcap.com/guide/npcap-devguide.html#npcap-feature-loopback Presumably you meant https://npcap.com/guide/npcap-devguide.html#npcap-feature-dot11 because https://npcap.com/guide/npcap-devguide.html#npcap-feature-loopback is for *loopback* adapters, not *802.11* adapters, and therefore does...

> I suspect this might be because of the Npcap driver's [`FilterClass`](https://docs.microsoft.com/en-us/windows-hardware/drivers/network/configuring-an-inf-file-for-a-modifying-filter-driver), which is "compression" and comes above "vpn" in the stack. This is complete conjecture at the moment, while...

> That could be analogous to the "any" pseudo-device from libpcap on Linux. Note that the closest analogue to the "any" device on Linux would be a way to plug...

Meaning that packets that arrive on the network adapter don't get seen by the network stack unless Npcap is capturing packets?