Site Boundaries and Boundary Groups

In Configuration Manager 2012 you can define one or more network locations called boundaries. 

A boundary in Configuration Manager 2012 can be based on the following types:

IP Subnet A boundary can be a subnet ID, which is automatically calculated while entering the IP subnet and subnet mask.
Active Directory Site When you are using Active Directory sites in your Active Directory domain, you can configure the boundary to use an Active Directory site.
IPv6 Prefix If you are configuring Configuration Manager 2012 in an IPv6 environment, you can configure a boundary to use an IPv6 prefix. An IPv6 prefix is a fixed part of the IPv6 address or the network ID.
IP Address Range Instead of using an IP subnet, you can configure the boundary to use an IP address range. The IP address range can be defined according to your needs.

The boundaries can contain devices that you want to manage with Configuration Manager 2012. Each boundary must be a member of one or more boundary groups, which are collections of boundaries. Boundaries are available for the Configuration Manager 2012 hierarchy, whereas boundaries in Configuration Manager 2007 were site specific.

New for clients is that before clients can identify an assigned site or locate content on a distribution point, a boundary must be associated with a boundary group. The boundary group is used for clients to find their assigned site, and they are used to locate content. In a boundary group you can associate system servers that have distribution points or state migration points installed so that the client can find software like applications, operating system images, and software updates. Boundary groups can be added to keep boundaries organized in a logical way.

Boundary creation can be done by hand, but when you enable the Active Directory Forest Discovery feature, you can create Active Directory site boundaries and IP subnet boundaries automatically at the same time. This process can be configured to run periodically. When migrating from Configuration Manager 2007, boundaries and boundary groups are also automatically created during the migration process.

A boundary group can be assigned to a specific site and can have one or more content locations. A distribution point can be added to one or more boundary groups. The boundary groups will provide the clients with a list of distribution points to download the content from. The client will choose the nearest distribution point.