Installation on private network

[Raymond Owens]

I have a freebsd system which is on a private network, there is no path to the internet. I am looking for methods to update the system to a new version level under these situations. Is there someway to synchronize the sources by burning a CD,  without being able to employ CVSsup or similar? I see how to bring ports over manually and how to do simple kernal option changes, my question is in regard to going from O/S version 6.0 to 6.1 or 6.1 to 6.1 stable .  Thanks.