H3C Technologies H3C MSR 50 - Manual (Page 342)

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Figure 327 Port roles
In Figure 327 , devices A, B, C, and D constitute an MST region. Port 1 and port 2 of device A are
connected to the common root bridge, port 5 and port 6 of device C form a loop, and port 3 and port
4 of Device D are connected downstream to the other MST regions.
Port states
In MSTP, the following states are available for a port:
• Forwarding—The port learns MAC addresses and forwards user traffic.
• Learning—The port learns MAC addresses but does not forward user traffic.
• Discarding—The port does not learn MAC addresses or forwards user traffic.
A port can have different port states in different MSTIs. A port state is not exclusively associated with a
port role. Table 143 lists the port states supported by each port role. ("√" indicates that the port state is
available for the corresponding port role and "—" indicates that the port state is not available for the
corresponding port role.)
Table 143 Ports states supported by different port roles
Port state
Port role
Root port/master
port
Designated
port
Boundary port Alternate port Backup port
Forwarding √ √ √ — —
Learning √ √ √ — —
Discarding √ √ √ √ √
Connecting to the common
root bridge
Boundary port
Port 1
Master port Alternate port
Designated port
A
B C
D
Backup port
MST region
Port 2
Port 6
Port 5
Port 4 Port 3