I was doing a side-by-side migration of sccm 2007 to sccm 2012 in my environment. I migrated the collections and enabled discovery of the AD forest and network. In the discovery option, I disabled the option to create new boundaries. I have not enabled any options to push out the 2012 clients, such as site pushes, SUP pushes, or scripts with GPOs. All my site servers have 1 subnet assigned to it; however, I noticed that all the computers across multiple subnets in my domain have either been upgraded to the sccm 2012 client or installed on a computer that did not previously have any clients. When I checked the logs on a computer with a newly installed sccm 2012 client, I see that the source of the installation is from the ip address that corresponds to the sccm 2012 server. The clients are also configured with the site code that corresponds to a primary site (which, again, is not assigned to any boundary that contains these clients).
What other methods are there that can automate the installation of these clients? Are there logs on the server or clients that can tell me where these updates are coming from?