Huawei Quidway S3000 Series Operation Manual page 27

Operation Manual - STP
Quidway S3000 Series Ethernet Switches
IV. CST
Common Spanning Tree (CST): Connects the spanning trees of all the MST region.
Taking every MST region as a "switch", the CST can be regarded as their spanning tree
generated with STP/RSTP. For example, the red line indicates the CST in figure2-1.
V. CIST
CIST (Common and Internal Spanning Tree): A single spanning tree made of IST and
CST (Common Spanning Tree). CIST of figure2-1 is composed by each IST in every
MST region and the CST.
VI. MSTI
Multiple Spanning Tree Instance (MSTI): Multiple spanning trees can be generated with
MSTP in an MSTI and independent of one another. Such a spanning tree is called an
MSTI. Every MST region can have many STI called MSTI. These STI is related to
corresponding VLAN.
VII. Region root
The region root refers to the root of the IST and MSTI of the MST region. The spanning
trees in an MST region have different topology and their region roots may also be
different. In each MST region in Figure2-1, every STI has its region root.
VIII. Common Root Bridge
The Common Root Bridge refers to the root bridge of CIST. There is only one common
root bridge in the specified network.
IX. Edge port
The edge port refers to the port located at the MST region edge, connecting different
MST regions, MST region and STP region, or MST region and RSTP region. For MSTP
calculation, the edge port shall take the same role on MSTI and CIST instance. For
example, the edge port as a master port on CIST instance should serve as a master
port on every MSTI in the region.
X. Port role
In the process of MSTP calculation, a port can serve as a designated port, root port,
master port, Alternate port, or BACKUP.
The root port is the one through which the data are forwarded to the root.
The designated port is the one through which the data are forwarded to the
downstream network segment or switch.
2-3
Chapter 1 RSTP Configuration