Software Update Services allow your server to cache updates from Apple and then redistribute them to clients within your organization. Now, this is going to greatly cut down on the amount of bandwidth consumed when new software patches are released. But if you have a large distributed organization you might want to have multiple Software Update Servers daisy-chained together in a cascade to download updates from each other and provide updates to sets of clients (maybe they’re geographically separated or you just have too many clients to provide updates to for just one server). Cascading the Software Update Services would further conserve bandwidth in your environment if you have multiple Software Update Servers.
In order to cascade Software Updates from one server to another you would first setup your first Software Update Server. Let’s say that we set it up as SUS1.domain.com and set it to run on port 8080. Next you would setup your second server (let’s call it SUS2.domain.com) and edit the “metaindexURL” key (by default it’s set to be swscan.apple.com) of the file, /etc/swupd/swupd.plist. So you would change the key to be SUS1.domain.com/content/meta/mirror-config-1.plist.
