Figure 5-8 Mstp Topological Structure; Table 5-1 Port Role And Port State - Zte ZXR10 2900E series Configuration Manual

Figure 5-8 MSTP Topological Structure

The ports have different roles:
l
Master: The port type is introduced in the MSTP protocol. When multiple different
areas exist, the master port is the port with the minimal cost to the root.
l
Root: The port that has the minimal cost to the root bridge and takes charge in
forwarding data to the root node. When multiple ports have the same cost to the root
bridge, the port with the lowest port priority becomes to the root port.
l
Designated: The port transmits data to the switch downward, and sends the STP
protocol message to maintain the state of STP.
l
Backup: The port receives the STP message, which proves that there exists a loop
to the port itself.
l
Alternate: The port receives excess STP protocol messages from other equipment.
However, when the original link fails, the port becomes transmitting and maintains the
network taking the place of the faulty port.
l
Edged: The port is used to connect the terminal equipment, for example, PC. The
port does not participate in the calculation before the STP is stable, and the state can
be switched fast.
According to the port role, the port state is different after the calculation becomes steady.
For the relationships between the port role and the port state, refer to

Table 5-1 Port Role and Port State

Port Role
Master
Root
Designated
Backup
SJ-20130731155059-002|2013-11-27 (R1.0)
Chapter 5 Service Configuration
Port State
Forward
Forward
Forward
Discard
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Table 5-1.