Chapter 7
| Spanning Tree Algorithm
Displaying Interface Settings for STA
– 222 –
The rules defining port status are:
â–
A port on a network segment with no other STA compliant bridging device
is always forwarding.
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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.
â–
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 Admin Link Type in STA
Port Configuration on page 217.
◆ Oper Edge Port – This parameter is initialized to the setting for Admin Edge
Port in STA Port Configuration on page 217 (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.
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