HP V1910 manual Port states, Port roles, 188

∙Designated port: Forwards data to the downstream network segment or device.

∙Master port: A port on the shortest path from the local MST region to the common root bridge, connecting the MST region to the common root bridge. If the region is seen as a node, the master port is the root port of the region on the CST. The master port is a root port on IST or CIST and still a master port on the other MSTIs.

∙Alternate port: The backup port for a root port and master port. When the root port or master port is blocked, the alternate port takes over.

∙Backup port: The backup port of a designated port. When the designated port is invalid, the backup port becomes a new designated port and starts forwarding data without delay. A loop occurs when two ports of the same MSTP device are interconnected, so the device blocks one of the ports. The blocked port acts as the backup.

A port can play different roles in different MSTIs.

a.Port roles

Connecting to the common root bridge

MST region	Port 1
	Master port

A

Port 2

Alternate port

B

C

Port 5

Port 6

Designated port Port 3

Backup port

D

Port 4

In a, 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.

Port states

In MSTP, a port may be in one of the following states:

∙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.

NOTE:

When in different MSTIs, a port can be in different states.

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