What is a Boundary?
If you see the map of your country, you will notice that all the states are divided with a line, also known as the boundary. Why are they divided? Because every state may have its own policies and access to its own separate resources which are within that region. It is the same for SCCM.
In multi-regional environments, you will have to deal with machines belonging to multiple states or even countries. Machines belonging to a region would ideally want to access resources (like content, policies, etc.) that are either within the same region or nearest to that region. This is achieved through the concept of Boundaries and Boundary Groups.
Boundaries are used to group a set of machines that have something in common. They can be machines on the same floor of an office, or machines having the same Active Directory site assigned, etc. Boundary Groups, on the other hand, are used to configure the Site System Servers (like MP, DP, SUP), which those machines will try to access, when looking for policies, content, etc. They are also used for automatic Site assignment on the machines present within those Boundaries.
We can add more than one Boundary to a Boundary Group. So machines present in three different buildings (three different Boundaries) in the same region can have access to the same resources (using one Boundary Group).
Configuration
Boundary and Boundary group creation is done from the “Administration” node in the SCCM Console.


Creating a Boundary
Right-click on “Boundaries” and select “Create Boundary” to start the creation process.

As you can see above, I have selected the Boundary Type as “IP address range” and gave the required values. Now any machine having an IP address in the given range will belong to this Boundary.
Creating a Boundary Group
Right-click on “Boundary Groups” and select “Create Boundary Group” to start the creation process.

In the above screenshot, I have added the name of the Boundary Group along with a description and by clicking the “Add” button at the bottom, I have also added the IP range boundary which I just created. Now that boundary and all machines which lie in that boundary belong to this Boundary Group. But all this will be of no use until and unless we move on to the next step to configure automatic site assignment and Site System Server assignment.

If you click on the “References” tab of the same window, you’ll be able to add those configurations. Automatic Site Assignment can be done by just checking the highlighted checkbox and selecting the required Site through the drop-down box. The appropriate Site Servers can be added by clicking on the “Add” button and selecting the servers from a list. These Site Servers are going to be used by the machines in the IP range boundary to download content or policies or updates. So it’s best to select the Site Servers which are either located in the same region or nearest to the region where the machines are located in order to get the best performance.