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Troubleshooting Network Sharing Issues: Part 1

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Even if you can't share files among any computers on the network or you just have a single problem PC, Eric Geier shows you how to get sharing again. In part I, you'll see how to refresh your networking gear and verify that the sharing, firewall, and router settings are correctly configured. Before you revert back to using USB drives or 3-1/2-inch floppies to transfer files, review the troubleshooting tasks and techniques in this two-part series.
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Computer problems can be very annoying—especially network and sharing issues. There are many aspects in networking where problems can arise. For example, there are settings that you or others might fiddle with that can prevent users from seeing each other's files.

Some settings just might not be configured correctly from the get-go. Windows and the underlying networking technology can also have problems.

Whatever the underlying issue, in this two-part tutorial, we'll review troubleshooting tasks and techniques to get computers sharing among each other again.

We'll start with refreshing the network, rebooting computers and networking gear. We'll also make sure that sharing, firewall, and router settings are properly configured.

Starting with the Basics

As with other computer problems, glitches might work themselves out when the equipment is refreshed. Depending upon the issues you're experiencing, restarting your computers and router might fix your sharing problems.

If you're having problems sharing among all the networked computers, first try to reboot the router. If you are having problems with only a select computer or two, restart them and see if it helps bring them back online.

Rebooting your router simply consists of unplugging it from the wall, waiting a couple of seconds, and plugging it back in. For computers, restart them as you would any other day. If you'd rather not wait for a full restart, you could first try to refresh the network adapter. From the Control Panel or networking interfaces, open the Network Connections window. Then right-click the network connection/adapter icon, select Disable (see Figure 1), wait a couple of seconds, right-click the icon again, and choose Enable. Sometimes this helps fix glitches preventing sharing, whether it's from restarting the adapter or forcing it to reconnect with the network.

Ensure that File and Printer Sharing is Enabled

On Windows computers, the sharing protocols for network connections or adapters must be enabled for that particular computer to host and access network shares. Although firewall configurations and other settings might be enabled, sharing is not possible unless these protocols are enabled.

The File and Printer Sharing for Microsoft Networks protocol enables remote users to access shares on the computer. The Client for Microsoft Networks protocol gives the computer the ability to access other network shares.

You can double-check to see whether the sharing protocols are enabled from a network connection's properties dialog box, as shown in Figure 2.

From the Control Panel, click Network Connections, right-click a connection, and select Properties.

If you get the following error message when trying to enable these protocols, uninstall the adapter from Device Manager, reboot, and if necessary, manually reinstall the adapter:

  • "Your current selection will also disable the following components: Client for Microsoft Networks. Are you sure you want to disable these component(s)?"

Check Windows Firewall

Computers use firewall software to control the type of traffic that's allowed in and out of the network adapter. In addition to preventing hacking attempts, firewalls can also prevent you from sharing. Windows Firewall, Microsoft's built-in tool, is supposed to be automatically configured by Windows when sharing is enabled, but the settings can be manually changed.

If you are having problems accessing shares on a particular computer, you should verify its firewall configuration. In addition to Windows Firewall, double-check any third-party firewall utilities that may have been installed with anti-virus or Internet security solutions.

In Windows Firewall, accessible via the Control Panel (or Network and Sharing Center in Vista), you'll see a File and Printer Sharing entry (see Figure 3). When viewing the Exceptions list; make sure this is checked.

The exact configuration options for third-party utilities vary. Some may first require you to define the network as safe. Some may have a sharing setting similar to Windows Firewall. If it requires you to input port numbers, you need to open UDP ports 135–139 and TCP ports 135–139.

Check the Windows Vista sharing settings

Microsoft introduced new networking settings in Windows Vista, which let you better manage your network and sharing preferences. These are all accessible from the Network and Sharing Center (see Figure 4). To open it, right-click the network icon in the system tray and select Network and Sharing Center.

First, you should make sure that the network is classified correctly. The classification type (Public or Private) is shown next to the network name on the Network and Sharing Center.

You initially choose the network type the first time you connect to the network; however, you can change it later by clicking the Customize link to the right of the network name and type it in.

By default, when on a public network, Vista disables sharing. If on a private network, Vista uses the settings you define, which are the Sharing and Discovery settings you see just below the network connection information. To ensure that sharing is possible, at least enable the first two options: Network Discovery and File Sharing.

Check the Router Settings

Most routers have a feature that you can enable to prevent communication among users, which is great when setting up a public network. Vendors use different names for this feature, including AP isolation, layer-2 isolation, and WLAN partition. If this feature has been enabled, sharing won't work.

If you can't share among any computers on the network, you should double-check for this feature's existence and status. Start by logging in to your router's web-based utility by using its IP address. If available, you should find the feature in the basic or advanced wireless settings.

Stay tuned—in the next part, we'll verify the sharing and file (NTFS) permissions; discover how to manually access shares; and, as a last resort, reinstall adapters and restore the router to its factory defaults.

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