Information on how to debug your Preferred Server configuration can be found here

http://community.landesk.com/support/docs/DOC-27151

For LDMS 9.0 and Newer Versions

Preferred Servers can be enabled in the LANDesk Console.  It now includes the ability to authenticate to a UNC share or a web share using the credentials configured for the preferred package server.  That way, when the share is accessed by an Agent workstation's Local System account, it will be able to access the share using the credentials specified instead of simply trying to authenticate as Local System.

1. In the LANDesk Console, click Tools | Distribution | Content Replication/Preferred Servers.
2. Click Add to add a new server, or click an existing entry and click Edit.
3. Enter the server information.
4. Click Test credentials to make sure the credentials you provided work.
   1. (Optional) If you want to use IP address ranges to lilmit which clients you want using this server as a preferred server, click on "IP address ranges" enter the the IP addresses and click Add.
      
5. Click Save.

For all versions of LDMS, the package server must have the exact same share name and directory structure as the source referenced in the distribution package. This works for both UNC and URL paths.  The folder structure on the Package Server must reflect the structure on that of the core server.

For example, if the packages on the core server can be found here:

CoreServer\packages\

Then on the package server called PackageServer, they should be found here:

PackageServer\packages\.

For web it is similar:

The preferred server settings are automatically updated on the clients every 24 hours. These settings are stored in the file %ProgramFiles%\LANDesk\ldclient\sdmcache\preferredservers.CoreServerName.dat

For LDMS 8.7 and 8.8

Preferred Servers can be enabled in the LANDesk Console.  It now includes the ability to authenticate to a UNC share or a web share using the credentials configured for the preferred package server.  That way, when the share is accessed by an Agent workstation's Local System account, it will be able to access the share using the credentials specified instead of simply trying to authenticate as Local System.

1. In the LANDesk Console, click Configure | Preferred server.

2. Click Add to add a new server, or click an existing entry and click Edit.

3. Enter the server information. If you want to use IP address ranges that you want this server to be available to, enter them and click Add.

4. Click Test credentials to make sure the credentials you provided work.

5. Click OK.

For all versions of LDMS, the package server must have the exact same share name and directory structure as the source referenced in the distribution package. This works for both UNC and URL paths.  The folder structure on the Package Server must reflect the structure on that of the core server.

For example, if the packages on the core server can be found here:

CoreServer\packages\

Then on the package server called PackageServer, they should be found here:

PackageServer\packages\.

For web it is similar:

The preferred server settings are automatically updated on the clients every 24 hours. These settings are stored in the file %ProgramFiles%\LANDesk\ldclient\sdmcache\preferredservers.dat

For LDMS 8.6.1 and Previous Versions

Modify this registry key on client machines:

HKEY_LOCAL_MACHINE\Software\LANDesk\ManagementSuite\WinClient\SoftwareDistribution\

Add a new string value named PreferredPackageServer. Set this to the name of the package server.

For  how to set up an HTTP share:

http://community.landesk.com/support/docs/DOC-6986