S
PANNING
T
REE
A
LGORITHM
12-14
- 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 the n 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 Lin k
Type in STA Port Configuration on page12-18.
•Oper Edge Port – This parameter is initialized to the setting for Admin
Edge Port in STA Port Configuration on page 12-18 (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 connecting the bridge to the root bridge (i.e., root
port), connecting a LAN through the bridge to the root bridge (i.e.,
designated port), or 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.