To load-balance the distribution of Software Update across multiple Software Update servers or to conserve bandwidth to the Internet, you can change the /Library/Server/Software Update/Config/swupd.plist file to redirect where your Software Update server obtains software updates.
By redirecting your Software Update server, you can have multiple Software Update servers on your private network. However, only one Software Update server needs access outside your private Intranet to obtain software updates from the Apple Software Update server. Then each additional server can access the internal server to obtain the software updates.
On your Software Update server, open Terminal (located in /Applications/Utilities/.
Use your preferred text editor to edit the /Library/Server/Software Update/Config/swupd.plist file.
Locate the following metaIndexURL key:
...<key>metaIndexURL</key><string>http://swscan.apple.com/content/meta/mirror-config-1.plist</string>Change the URL in the tags <string></string> to the location of your selected Software Update server.
For example:
<key>metaIndexURL</key><string>http://myserver.example.com:8088/catalogs.sucatalog</string>Save the changes and exit Terminal.