A Quick post
With System Center 2012 the CAS role was introduced ( Look at my previous post à
https://msandbu.wordpress.com/2012/05/30/sccm-2012-cas/ )
Since this is the role sits on top of the hierarchy it needed to sync its SUP/WSUS point directly with Microsoft Update.
In many cases, the CAS role might not even be connected to the internet or have limited connectivity, and with this came the challenge.
You had little or few options that you could use to connect your CAS server to Microsoft update, one of those options could be to use a proxy server between the CAS and Microsoft update. Another one would be to allow the CAS to only talk directly to the internet, but this is not always the best way to go.
But! With Service Pack 1 of System Center 2012 you now have the option to synchronize your CAS with an on-premise WSUS server, (this is one of the many changes in the hierarchy structure in SP1 refer to more of these articles on TechNet à
Starting in Configuration Manager SP1, you can install multiple software update points at a primary site. The first software update point that you install is configured as the synchronization source. This synchronizes from Microsoft Update or a WSUS server not in your Configuration Manager hierarchy. The other software update points at the site use the first software update point as the synchronization source.
Starting in Configuration Manager SP1, at the top-level site, you can specify as the synchronization source instead of Microsoft Update an existing WSUS server that is not in the Configuration Manager hierarchy.
Starting in Configuration Manager SP1, You can select from two built-in software update deployment templates from the Automatic Deployment Rule Wizard. The Definition Updates template provides common settings to use when you deploy definition software updates. The Patch Tuesday template provides common settings to use when you deploy software updates on a monthly cycle.