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Troubleshooting Network Sharing Issues
By Eric Geier (NoWiresSecurity Founder
& CEO) - originally published on
InformIT.com
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, 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.
Figure
1
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.
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.
Figure 3
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.
Figure 4
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.
Verify the Sharing Permissions
If you are having problems accessing
certain shares or are unable to modify shared files, you should
check the sharing permissions. These settings define who can access
the shared folder and what they can do with the files (read-only,
write, delete, etc).
The way you define the sharing permissions differs between using the
basic (default) sharing method and the advanced sharing method you
can manually enable.
You can bring up the sharing settings by right-clicking a folder and
choosing the sharing option. When verifying these settings, you want
to just make sure you have defined what you desire.
If users have only read-only access, and you want them to be able to
modify files, make sure that the sharing permissions are set
accordingly.
For example, in Windows XP's basic default sharing mode, this means
checking the Allow users to change files option, as seen in Figure
5.
Figure 5
When using the advanced sharing option in XP or Vista, this means
editing the access list and each user's permission type, (see Figure
6). The default simple sharing method in Vista is very similar to
the advanced method.
Figure 6
NOTE
For much more detail on setting permissions, see my previous article
in this series.
Verify the File (NTFS) Permissions
Separate permissions exist for local
file security, provided by the popular NTFS filesystem, which also
applies to the remote access of files on networks.
Thus incorrectly configured file permissions for folders or files
could also cause a sharing issue or outcome you don't desire. These
permissions are configurable similar to those for advanced sharing.
To access the settings, right-click a folder or file, click
Properties, and select the Security tab (see Figure 7).
Figure 7
In XP, advanced sharing must be enabled in order for the Security
tab to appear.
NOTE
To disable the basic sharing method and for more file permission
details, refer to Part I of this series.
Accessing Shares Manually
Sometimes the networking protocols
working in the background have hiccups and don't work correctly. If
you've checked the other possible holdups and still can't access a
shared computer, the protocols may not being properly resolving the
computer names.
To get around this common problem, you can manually access a
computer using what is called the uniform naming convention (UNC)
address/path of the computer.
If the computer isn't showing up in My Network Places in XP or
Network in Vista, you can use the computer name in the UNC address.
Alternatively, you can use the computer's IP address in the UNC
address.
Sometimes this does the trick when the protocols are messed up (the
computer shows up on the network, but you can't browse to it)
because My Network Places and Network use the computer name approach
by default.
To manually access a computer (or a shared folder or file directly),
type the UNC address into a web browser or a window.
As the following examples show, first type two backslashes and then
the desired computer name or IP address; plus the optional path for
the shared folder or file, separated by single backslashes.
•\\desktoppc: Brings up a listing of the computer's shares via the
computer name.
•\\192.168.0.105: Brings up a listing of the computer's shares, via
the computer's IP, such as the one seen in Figure 8.
•\\192.168.0.105\sharedfolder: Accesses a folder directly on the
same computer using the IP.
•\\desktoppc\sharedfolder\subfolder\: Accesses a subfolder of a
shared folder using the computer name.
•\\192.168.0.105\sharedfolder\exfile.doc: Directly accesses a file
within a shared folder using the IP.
Figure 8
Reinstalling Adapters and Restoring the Router
If you still can't share folders or
access shares, try reinstalling select adapters or restoring the
router to factory defaults.
If there's a particular problem computer, reinstall its adapter. If
the issue is network-wide, restore the router.
Reinstalling an adapter consists of uninstalling its driver and
installing it again. From either the Control Panel or by
right-clicking the Computer/My Computer icon, access the Device
Manager window.
Find the network adapter, right-click it, and select Uninstall, as
shown in Figure 9.
Figure 9
Now you should restart the computer. When it boots up, Windows
should automatically detect the adapter and reinstall it, with or
without you having to use the new hardware wizard.
Otherwise, if it's not recognized, follow the manufacturer's
installation instructions.
Restoring your router back to its factory defaults only takes a
couple of seconds, but remember that you have to reconfigure it.
Thus, you should first log on to the router's web-based utility by
typing its IP address into a browser and use the password you
created during the initial setup to log in (use the default password
if you didn't create one).
Browse around the utility to find where you can create a backup of
the router settings and then save the configuration file to your
computer.
You should also reference the adapter's documentation before
restoring to make sure that you have the default password for the
router because you'll have to use it after the restore.
When you're ready to restore the router, find the reset button or
hole on the router. (It's usually on the back of the router.) It
could be very small (you'll need to use a paper clip or something
similar) or large (you'll need only a pen).
Simply push the button, hold for 30 seconds, and release. You should
soon see the network in Windows, using the default network name with
no encryption or security, for wireless routers.
For wired connections, it should automatically reconnect. Now log
into the web-based utility, using the factory default password, and
use the backup file to restore your configurations.
Hopefully, your sharing issues are long gone!
Don't Give Up
We doubled-checked to see that the
sharing settings were enabled in the network connection properties,
firewall settings, and Vista's new Sharing and Discovery settings.
We also checked to see that the router was set to block all user
communication.
We verified that the sharing and file permissions were set to allow
access by the user(s) having issues accessing the share.
Finally, we discovered how to manually access shares using the
computer name or IP address.
These tasks root out most common problems that can mess up sharing
on a network. If you still have problems, contact the manufacturers
of your networking gear for more help.
Additionally, you can try to Google for help; use search terms to
describe the problem and the equipment model or make. |
