QTECH
Software Configuration Manual
15-195
Figure 5 Port roles
Figure 5 helps understand these concepts. Where,
·
Devices A, B, C, and D constitute an MST region.
·
Port 1 and port 2 of device A connect to the common root bridge.
·
Port 5 and port 6 of device C form a loop.
·
Port 3 and port 4 of device D connect downstream to other MST regions.
11) Port states
In MSTP, port states fall into the following tree :
·
Forwarding : the port learns MAC addresses and forwards user traffic;
·
Learning : the port learns MAC addresses but does not forwards user traffic;
·
Discarding : the port neither learns MAC addresses nor forwards user traffic.
&
Note :
When in different MST instances, a port can be in different states.
A port state is not exclusively associated with a port role. Table 6 lists the port state(s) supported by each
port role (“
√
” indicates that the port supports this state, while “-“ indicates that the port does not support this state).
Table 6
Ports states supported by different port roles
Role
State
Root
port/Master
port
Designated
port
Alternate port
Backup port
Forwarding
√
√
—
—
Learning
√
√
—
—
Discarding
√
√
√
√
