8- and 24-Port Gigabit L2 Managed Power-over-Ethernet (PoE) Switches
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Figure 4-149. STP port configuration.
Parameter description:
Port Status displays the current state of a port. We cannot manually set it because it displays the status only. There are three
possible states (according to the 802.1w specification):
DISCARDING state indicates that this port can neither forward packets nor contribute learning knowledge.
NOTE:
Three other states (Disable state, BLOCKING state, and LISTENING state) defined in the 802.1d specification are now all
represented as DISCARDING state.
LEARNING state indicates this port can now contribute its learning knowledge but still cannot forward packets.
FORWARDING state indicates this port can both contribute its learning knowledge and forward packets normally.
Path Cost Status: The value of the path through this port to Root Bridge. STP algorithm determines a best path to Root Bridge by
calculating the sum of path cost contributed by all ports on this path. A port with a smaller path cost value would most likely become
the Root Port.
Configured Path Cost: The range is 0– 200,000,000. In the switch, if path cost is set to zero, the STP will get the recommended value
resulting from auto-negotiation of the link accordingly and display this value in the Path Cost Status field. Otherwise, it may show the
value that the administrator set up in Configured Path Cost and Path Cost Status.
802.1w RSTP as the recommended value: (Valid range: 1– 200,000,000)
10 Mbps: 2,000,000
100 Mbps: 200,000
1 Gbps: 20,000
Default: 0
Priority: Priority here means Port Priority. Port Priority and Port Number are mixed to form the Port ID. Port IDs are often compared in
order to determine which port of a bridge would become the Root Port. The range is 0–240. The default is 128.
Admin Edge Port: If a user selects “Yes,” this port will be an edge port. An Edge Port is a port connected to a device that knows
nothing about STP or RSTP. Usually, the connected device is an end station. Edge Ports will immediately transition to the forwarding
state and skip the listening and learning state because the edge ports cannot create bridging loops in the network. This will expedite
the convergence. When the link on the edge port toggles, the STP topology remains unchanged. Unlike the designated port or root
port though, an edge port will transition to a normal spanning-tree port immediately if it receives a BPDU. The default is No.
Admin Point To Point: A port is a point-to-point link, from RSTP’s view, if it is in full-duplex mode. It is a shared link if it is in half-
duplex mode. RSTP fast convergence can only happen on point-to-point links and on edge ports. This can expedite the convergence
because this will cause the port to transition to forwarding state.
