Spanning Tree Algorithm
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Instruction Manual - NXA-ENET8-POE+
Displaying Interface Settings for STA
Use the Spanning Tree > STA (Configure Interface - Show Information) page to display the current status of ports or trunks in the
Spanning Tree.
The following table lists the options on this page:
Spanning Tree - STA Options
Spanning Tree
Shows if STA has been enabled on this interface.
BPDU Flooding
Shows if BPDUs will be flooded to other ports when spanning tree is disabled globally on the switch
or disabled on a specific port.
STA Status
Displays current state of this port within the Spanning Tree:
• Discarding - Port receives STA configuration messages, but does not forward packets.
• Learning - Port has transmitted configuration messages for an interval set by the Forward Delay
parameter without receiving contradictory information. Port address table is cleared, and the
port begins learning addresses.
• Forwarding - Port forwards packets, and continues learning addresses.
The rules defining port status are:
• A port on a network segment with no other STA compliant bridging device is always forwarding.
• If two ports of a switch are connected to the same segment and there is no other STA device
attached to this segment, the port with the smaller ID forwards packets and the other is
discarding.
• All ports are discarding when the switch is booted, then some of them change state to learning,
and then to forwarding.
Forward Transitions
The number of times this port has transitioned from the Learning state to the Forwarding state.
Designated Cost
The cost for a packet to travel from this port to the root in the current Spanning Tree
configuration. The slower the media, the higher the cost.
Designated Bridge
The bridge priority and MAC address of the device through which this port must communicate to
reach the root of the Spanning Tree.
Designated Port
The port priority and number of the port on the designated bridging device through which this
switch must communicate with the root of the Spanning Tree.
Oper Path Cost
The contribution of this port to the path cost of paths towards the spanning tree root which
include this port.
Oper Link Type
The operational point-to-point status of the LAN segment attached to this interface. This
parameter is determined by manual configuration or by auto-detection, as described for
in the Spanning Tree - STA Options table on page 108.
Oper Edge Port
This parameter is initialized to the setting for
in theSpanning Tree - STA
Options table on page 108 (i.e., true or false), but will be set to false if a BPDU is received,
indicating that another bridge is attached to this port.
Port Role
Roles are assigned according to whether the port is part of the active topology, that is the best
port connecting a non-root bridge to the root bridge (i.e., root port), connecting a LAN through
the bridge to the root bridge (i.e., designated port), is the MSTI regional root (i.e., master port), or
is an alternate or backup port that may provide connectivity if other bridges, bridge ports, or LANs
fail or are removed. The role is set to disabled (i.e., disabled port) if a port has no role within the
spanning tree.