Auto discovery, which automatically generates a graphical display and inventory of the computers on the network, is an expected feature in many network management products like The Dude. Now Auto Discovery is a built in feature of our favourite new operating system, Windows Vista. One of the shiniest features of Windows Vista is The Network Map - its ability to show you a semi graphical display of all of the computers, routers, and switches on the network.
The Network Map uses a new protocol - Link-Layer Topology Discovery (LLTD). Regardless of what firewalls, or other hardware or software protective devices we have on our network, LLTD discovers all devices connected. LLTD has basically the same strengths and weaknesses as other well known alternate protocols IPX/SPX and NetBEUI (neither of which are available for Vista).
* Regardless of what Windows Networking protocol you're using - IP, IPX/SPX, or NetBEUI, LLTD will show you a map of all computers running Windows Vista and Windows XP (when equipped).
* Regardless of what firewalls or routers you may have setup to segment your network, and protect some computers from others, LLTD will pass through to each segment, and will inventory all computers on the segment.
* Regardless of whether LLTD shows you a computer, you won't necessarily have the ability to access that computer, or even determine its network address, for Windows Networking.
The Network Map presents additional challenges.
* It is only available on Windows Vista (and Windows XP, with (KB922120): the optional LLTD Responder).
* Its availability, and the fact that "it simply works", can cause confusion among computer owners, who can't get Windows Networking to work, when a Windows Vista computer is installed.
* People confuse the Network Map with Windows Explorer, which provides a similar functionality, but will display different information.
It's a great tool, but you need to be aware of its limitations.
Source: PChuck's Network