3com 2928 User Guide

 

1-13 

Port roles 

Connecting to the 
common root bridge

Port 1

Port 2

Master port

Alternate port

Designated port

Port 3

Port 4

Port 5

A

B

C

D

Port 6

Backup port

 

 

In 

, 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, port 3 and port 4 of 
Device D are connected downstream to the other MST regions.  

In MSTP, port states fall into the following three: 

z

 

Forwarding: the port learns MAC addresses and forwards user traffic;  

z

 

Learning: the port learns MAC addresses but does not forward user traffic;  

z

 

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. 

 lists the port state(s) supported by 

each port role. (“√” indicates that the port state is available for the corresponding port role; “—” indicates 
that the port state is not available for the corresponding port role.)