HP 3100 Series Configuration Manual page 68

•
Designated port—Forwards data to the downstream network segment or device.
•
Alternate port—The backup port for a root port or 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 the new designated port. A loop occurs when two ports of the same
spanning tree device are interconnected, so the device blocks one of the ports. The blocked
port acts as the backup.
•
Edge port—An edge port does not connect to any network device or network segment, but
directly connects to a user host.
•
Master port—A port on the shortest path from the local MST region to the common root bridge.
The master port is not always located on the regional root. It is a root port on the IST or CIST
and still a master port on the other MSTIs.
•
Boundary port—Connects an MST region to another MST region or to an STP/RSTP-running
device. In MSTP calculation, a boundary port's role on an MSTI is consistent with its role on the
CIST. But that is not true with master ports. A master port on MSTIs is a root port on the CIST.
Port states
In MSTP, a port can be in one of the following states:
•
Forwarding—The port receives and sends BPDUs, obtains MAC addresses, and forwards
user traffic.
•
Learning—The port receives and sends BPDUs, obtains MAC addresses, but does not forward
user traffic. Learning is an intermediate port state.
•
Discarding—The port receives and sends BPDUs, but does not obtain MAC addresses or
forward user traffic.
When in different MSTIs, a port can be in different states. A port state is not exclusively associated
with a port role.
that the port supports this state, while a dash [—] indicates that the port does not support this state.)
Table 12 Port states that different port roles support
Port role
(right)
Port state
(below)
Forwarding
Learning
Discarding
Table 12 lists the port states that each port role supports. (A check mark [√] indicates
Root
port/master port
√
√
√
Designated port Alternate port
√ —
√ —
√ √
59
Backup port
—
—
√