Requirements for hosting a Software Update Server
DNS (Domain Naming Service)
The Software Update service requires that the server is registered in DNS and resolved correctly. The clients use the DNS name of the server to download updates.
Servers and ports
The synchronization module accesses the following public Software Update Servers on destination port 80:
The server (http://swcdn.apple.com) currently redirects to the Akamai content distribution network that hosts the updates. Note that the redirected IP address of http://swcdn.apple.com may vary over time or by geographic region.
With OS X Mountain Lion 10.8 or later, the synchronization module also accesses the following public Software Update Server on destination port 443:
Authenticated proxy server aren't supported by the synchronization module, which means that updates aren't mirrored by the server. The synchronization module may work with non-authenticated and transparent proxy servers, Apple recommends that the Software Update Server havehas direct access to the public Software Update Servers that are listed above.
Dedicated network connection to the Internet
The server must have a dedicated connection to the Internet to use Software Update Server. It's recommended that the server has direct access to the URLs that are listed above in the "Servers and ports" section. If Software Update Serve can't reach Apple's content servers, it will try again during the next scheduled sync, 24 hours later.