Diagnosing Problems Using Network

Network mapping, a feature that was new in Windows Vista, uses the Link Layer Topology Discovery (LLTD) protocol to find the other computers and devices on your network, and then displays them in a schematic representation . To display the map, in Network And Sharing Center click See Full Map . Figure 19-2 shows an example .

Computers with more than one network adapter create a separate map for each one

Computers with more than one network adapter create a separate map for each one

Figure 19-2 The computer you're using is always shown in the upper left corner of Network Map . Notice that the computer named Tequila has a wireless connection (represented by a dotted line) and a wired connection (represented by a solid line) to the router.

Network mapping works with wired and wireless networks, but only on private (home or work) network locations; by default, you can't view a map of a domain-based network or a public network. LLTD maps only the computers in a single subnet—the typical setup in a home or small office .

You might notice that some computers and devices are shown separately at the bottom of the window, or they might be missing altogether. (For example, the Hpserver device at the bottom of the display shown in Figure 19-2 is a server running Windows Home Server, which supports UPnP but not LLTD.) This occurs because not all operating systems and devices include LLTD support, or because the devices might not be configured properly.

INSIDE OUT

Use Network Map on a domain computer

By making changes through Group Policy, you can enable network mapping on domains, public networks, or both. To make this change, follow these steps:

1. At a command prompt, type gpedit.msc to open the Local Group Policy Editor. (The Local Group Policy Editor is available on computers running the Professional, Enterprise, or Ultimate edition of Windows 7 . These are also the only editions that can join a domain.)

2. Navigate to Computer Configuration\Administrative Templates\Network\ Link-Layer Topology Discovery.

3. Double-click the Turn On Mapper I/O (LLTDIO) Driver policy.

4. Select Enabled, and then select Allow Operation While In Domain.

5. Click Next Setting .

6. Repeat the selections for the Turn On Responder (RSPNDR) Driver policy setting, and then click OK.

Note that, depending on the size of the network, creating a network map on a domain-based network can be inordinately slow, which is why it is disabled by default. Note also that you can use these same policy settings to enable network mapping on a public network and, if you want, disable network mapping on a private network . For security and convenience, we don't recommend either of these options .

Devices shown at the bottom generally fall into one of the following categories:

• Computers running Windows XP LLTD is installed by default in Windows 7 and Windows Vista, but it is not included in earlier Windows versions. An LLTD client is available for Windows XP, and it should be available through Windows Update. (To find out if it's installed, look at the properties for the network connection and see if LLTD appears in the list of installed protocols.) You can download and install the protocol without Windows Update; for details, see Knowledge Base article 922120

Cw7io.com/1902). Note that if you have already installed Service Pack 3 for Windows XP, you'll need the hotfix available from w7io.com/1905. LLTD is not currently available for other versions of Windows.

• Other network devices LLTD (along with another network discovery-related technology, Plug and Play Extensions, or PnP-X) is part of the Windows Rally technologies, an initiative for network hardware devices that gained steam in 2006. Devices that include LLTD support became widely available in 2007 and later, but earlier devices are not fully recognized by Network Map. Most devices sold in recent years support UPnP, which should get the device somewhere in the map window; however, Network Map displays only limited information about the device and offers only limited control of the device.

• Configuration problems In Network And Sharing Center, be sure that your network is not identified as a public network, and be sure that network discovery is turned on. In Network Connections, view the properties of your network connection and be sure that two LLTD-related protocols, Link Layer Topology Discovery Mapper I/O Driver and Link Layer Topology Discovery Responder, are installed and enabled (that is, their check boxes are selected). Whether you use Windows Firewall or another firewall, be sure it has an exception enabled for file and printer sharing.

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