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Mapped Resources (Drives/Printers)

Posted on 2011-02-21
Medium Priority
Last Modified: 2012-05-11
We have currenly moving users to a new Active Directory structure.  All things are now being controlled through AD when it comes to mapping printers and network drives.

We have some users losing some of their Drives and Printers randomly throughout the day.  It has been verified Client Side Extensions are installed.  Clients are mostly XP with one maybe two of the clients involved have Windows 7.

Can you think of any reason this may be happening?
Question by:m698322h
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Expert Comment

ID: 34945435
I know I have seen this kind of thing at our location as well.    We started mapping the network drives with the fully qualified domain name in login script.  ("server.domain.com\share")  I don't think i have been seeing that as much as before.  I wonder if it will help you.   Good luck.

Accepted Solution

Vanguard_LH earned 2000 total points
ID: 34946104
Mapped resources can be dropped either due to idle timeouts configured on the other host or simply due to network problems.  Unless you wrap a program that uses a mapped resource with a batch file that runs the 'net use' command to ensure the mapping is current and active, you can't guarantee the mapping will be there later.  Microsoft sets the idle timeout to 15 minutes to preserve system resources on the target host.  That means the mapping has to reestablish an active connection when later used but the target host may be too busy, not have the resources, or there is a networking problem when you later attempt to reconnect.  You can't even be sure the inital mapping was successful and the later attempt to reestablish a connection may fail.


Users may elect to map to networked resources or you could push login scripts to their hosts that does the mapping, but you're still stuck with mapped resources getting dropped during a Windows session.  Don't rely on a mapped resource being available simply because it was defined earlier.  If you specify a UNC path to the resource (i.e., forced to use mapping that gives drive letters to a file server) then use a batch file as a wrapper to a program that uses 'net use <drive> <uncpath>' before the program that needs the mapped resource, check the errorlevel returned to determine if you run the next command or exit the batch file, runs the program, and after the program exits then uses 'net use <drive> /delete' to get rid of the otherwise superfluous mapping.

Why not use UNC pathing to identify the networked resources?  Some old programs don't support UNC paths for resources but then maybe you don't have to use those old programs.

You posted here in a Windows XP group.  If Windows Vista or 7 were involved, another problem is its new TCP on-the-fly tuning features which can cause problems with other devices in the network that don't support TCP window scaling.  See http://support.microsoft.com/kb/935400.  It isn't just large e-mails that can have problems but also when copying huge files to a network resource, so you would use the mentioned netsh command to disable Vista's autotuninglevel feature.  You need to reboot after changing the value.  Apparently Microsoft changed the default value in an update that sets it to highlyrestricted; however, some users have noted they cannot change the value after applying Vista SP1 until they first run "netsh, interface, tcp, set heuristics disabled, set global autotuninglevel=disabled, quit".

Author Comment

ID: 34951607
Does any of this help if the item just up and disappears.  They do not get an "X" through it, just goes away like they delete it.

Expert Comment

ID: 34953908
Are the users that lose the mappings also rebooting their hosts or logging out and back in throughout the day?  If the mapping doesn't "take" because the target host is unreachable or unresponsive then the mapping will fail.  The failed mappings won't show up in Windows Explorer but they may work later when using a shortcut that does the mapping at that time.

Also, I forgot to mention that when using mapped resources that the Windows login could take a lot longer.  For every mapping, the user's host is going to try to reconnect to the mapped resource.  Many users will ask why their logins take so long when it turns out the mappings are taking a long time to establish.

Were the mappings made persistent?  Is the "Reconnnect at logon" option selected for the mapped resource?  If using a login script to do the mappings, are you using the 'persistent' parameter, as in "net use <uncpath> * /user:<domain>\<username> /PERSISTENT:yes"?  I don't know if the /user parameter is needed but you should be using the /persistent parameter for the mappings to survive across logins.  The asterisk says for all devices so presumably this makes the connection persistent for all existing mappings; else, you'll have to specify the device as you define the mapping to it.  I've heard that the checkbox "Reconnect at logon" sometimes isn't obeyed but the login script will work across logins (an example regarding Win7: http://www.gadgetgrill.com.au/2009/11/19/windows-7-fixing-the-mapped-drive-credentials-problem/).  Of course, just because you request a mapping doesn't mean it will work so maybe you should test the errorlevel returned from "net use" and if non-zero then add a comment into a logfile.  I suppose you could also redirect the output of the "net use" command into the logfile so you had some better info as to why the mapping failed.

What security software is installed on the problematic hosts (anti-virus, firewall, etc)?  Some firewalls, for example, can be configured to keep the network interface disabled until they have become fully active.  This means network access is disabled until the firewall decides it is fully ready to throttle access to the network.  If the firewall takes longer to get ready than to run the login script that does the mapping or persistent maps get reestablished after a login then there won't be any network access at the time the mappings are defined or attempted to get reestablished.  See if the software firewall on these hosts has an option to disable network access until it is ready; if so, disable that option and reboot.

Did you switch on "Always wait for network at computer start up and logon" in Group Policies?

To ensure there isn't some corruption in the encrypted registry area holding the cached login credentials, in Windows XP, run "control.exe userpasswords2", Advanced tab, Manage Passwords.  Delete all the network credentials which will mean the user may have to enter them again but hopefully just once.  In Vista, you go to Control Panel -> User Accounts and Family Safety -> Credential Manager.  Or might you be mapping a domain-controlled share using different credentials than what the user logs in with?  In that case, I'm lost since I have never had to manage a domain or the PDC.

Are the mapped resources in a different domain?  If so, you need to include the host's name before the login credentials, like:

username = <otherdomain>\<username>
password = <userpassword>

This would be the same when the user is at the login prompt and wants to log into a different domain.  The default when not specifying the domain would be:

username = <localmachine>\<username>
password = <userpassword>

If the networked resource cannot be added to a domain (e.g., Apple AirPort with attached drives) then, for example, in the Credential Manager you would use:

username = \<username>
password = <userpassword>

The leading slash eliminates using the current domain or machine name as a domain name in the login.

Isn't network troubleshooting fun?  Grrr.

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