CIST Root Port

The port on the CIST regional root bridge that connects to the CIST root bridge is the CIST root port (also known as the master port for MSTIs).

The CIST root port is the master port for all MSTIs in that region, and it is the only port that connects the entire region to the CIST root.

If a bridge is both the CIST root bridge and the CIST regional root bridge, there is no CIST root port on that bridge.