First things first: I know that you can install a sort-of-a Loopback Adapter in Windows.

But what I really found strange is that there exists nothing like lo on Windows. At all. From The missing network loopback interface:

Windows TCP/IP stack does not implement a network loopback interface, as found in other TCP/IP stack like lo* interfaces in BSD systems.


The Microsoft Loopback Adapter can be installed on Windows systems, to run network applications when no physical adapter is present or active on the system. This adapter is not the equivalent of a network loopback interface and IPv4 address can not be assigned to it. Also, it is not possible to sniff network traffic on it, at least with WinPcap.

I'd be really interested if somebody knew why this choice was made or why it never seemed necessary to include a loopback device in Windows. Because it comes in so handy to be actually able to capture packets you send from/to it in order to develop or debug network applications.

So if anybody has an experience in networking, TCP/IP stacks, etc. and is able to provide some insight, that would be much appreciated.

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  • Its there, just not installed by default in Windows...sevenforums.com/network-sharing/… – Moab May 4 '11 at 20:16
  • Yeah, no, see the first link in my question. I know it's sort of a loopback adapter, but you still can't just capture from it. – slhck May 4 '11 at 20:25
  • What background are you speaking from? If a programming background then spin it as a programming question and ask on Stackoverflow. – barlop May 5 '11 at 8:02
  • Does wireshark not pick it up? – barlop May 5 '11 at 8:06
  • @barlop No, it's not programming related. My question is why they chose not to implement it in a "proper" or otherwise useful way. Wireshark can't pick it up as WinPcap can't. – slhck May 5 '11 at 8:20

Historical reasons. From the ground up unix/linux has always been about the network. Whereas MS-DOS/Windows bolted the network on as an afterthought, initially with Windows own 'NetBIOS' rather than TCPIP.

Only when Netscape came along was it necessary for Microsoft to install a TCPIP stack and acknowledge the presence of the Internet. Before then you had to put your own stack together for talking to unix machines, paying handsomely for the privilege.

I hope this historical context goes some way to helping you understand why it is that MS-Windows is not really there yet when it comes to proper networking. To take a car analogy it is a bit like asking why motorbikes don't have four wheels. (Yes, that is a very poor analogy...)

Before it became important to get online there were many LAN protocols - DECnet, Token Ring, Novell stuff and Microsoft's effort that came with Windows 3.11 - only true experts could get these different boxes to talk together and networking was a truly dark art.

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    "From the ground up" - are you sure that the very first versions of Unix had networking capability? Also, at the time of Netscape, Microsoft did not have a TCPIP stack - you had to install your own. – John Saunders Jan 24 '15 at 17:50

Seriously? Are you certain that doesn't work?

It's a requirement that 127.0.0.X is routed to the same computer. It's part of the IPV4 standard. If Microsoft isn't implementing it, it's breaking spec and I'd find that surprising since "Microsoft"'s TCP/IP stack is really the BSD stack and I know they implement it.

I know that "lo" isn't listed as an interface, but that doesn't matter. It's just a shortcut anyhow.

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