H3C S5100-SI Series Operation Manual page 236

Operation Manual – MSTP
H3C S5100-SI/EI Series Ethernet Switches
switch C form a loop. Port 3 and port 4 on switch D connect downstream to other MST
regions. This figure shows the roles these ports play.
Note:
A port can play different roles in different MSTIs.
The role a region boundary port plays in an MSTI is consistent with the role it plays
in the CIST. The master port, which is a root port in the CIST while a master port in
the other MSTIs, is an exception.
For example, in
port in the CIST while a master port in all the other MSTIs in the region.
MST region
Figure 1-5 Port roles
X. Port state
In MSTP, a port can be in one of the following three states:
Forwarding state. Ports in this state can forward user packets and receive/send
BPDU packets.
Learning state. Ports in this state can receive/send BPDU packets but do not
forward user packets.
Discarding state. Ports in this state can only receive BPDU packets.
Port roles and port states are not mutually dependent.
combinations of port states and port roles.
Figure 1-5, port 1 on switch A is a region boundary port. It is a root
Connecting to the
common root bridge
Region boundary ports
Port 1
Master port
B
Designated port
Port 3
Port 2
Alternate port
A
C
Port 5
Backup port
D
Port 4
1-15
Chapter 1 MSTP Configuration
Port 6
Table 1-6 lists possible