Expand SCCM CB Primary site with CAS

If you are planning to expand SCCM Current branch site with CAS, it is not a simple running Setup.exe from install media. If you try to install using setup.exe from newly downloaded ISO, the install will fail with multiple different error MSG’s.
This short Expand SCCM CB Primary site with CAS article will explain how to add a CAS to existing primary SCCM site;

Prepare the environment to install CAS;
- If you have installed service connection point role on Primary site, then remove this from primary
- Give NT SYSTEM account to sa permissions on existing DB
- Make sure the listener of SQL Always On Availability Group for primary site server (if using SQL     always on) is pingable from all the servers

Installing CAS;
- Copy the CD.latest folder from existing primary to the CAS
- Install CAS select option to add existing site server to this hierarchy
- Use standalone SQL at this stage
- Once the installation completed, wait for the replication to be completed
- Configure SQL Always On for CAS then move the CAS to Always On Availability Group

At this stage PRI and CAS will be Always On Availability Group.