Qtech QSW-3900-2x10GE [196/245] When in different mst instances a port can be in different states

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 √ √ √ √