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7-3
SPANNING TREE
Root Cost indicates the cost (value), of the data path from the
FDMMIM to the Root bridge. The Root Cost value does not represent
a particular type of unit. It is simply a value that is compared to the
Root Cost value of other bridges in the network. The Root Cost is
used by STA when choosing a Root bridge. By editing the Path Cost
parameter in the Port Parameters screen, you can influence the
selection of the Root bridge. The Root bridge’s Root Path Cost is 0.
Root Port displays the port identifier for the port that provides the
lowest cost path to the Root.
Hello Time indicates, in seconds, the length of time the Root bridge,
or bridge attempting to become the Root, waits before resending a
Configuration BPDU. The Hello Time is set by the Root bridge.
Bridge Max Age shows the setting for the FDMMIM’s BPDU
ageing timer. The ageing timer defines the maximum length of time
that a Configuration BPDU is retained by the bridge before it is
discarded. During normal operation, each bridge in the network
receives a new Configuration BPDU before the ageing timer expires.
If the timer expires before a new Configuration BPDU is received, it
indicates that the former Root is no longer active. The remaining
bridges begin Spanning Tree operation to select a new Root. The
Bridge Max Age is set by the Root bridge. You can edit the Bridge
Max Age value but, unless the FDMMIM is the Root bridge, the new
value has no effect. The new value becomes effective only when the
FDMMIM becomes the Root. (Default = 20 seconds. The allowable
range is 6 to 40 seconds.)
Bridge Forward Delay is the length of time that the FDMMIM
spends in the Listening or Learning state (listening to Topology
Change BPDU activity on the network) when moving toward the
Forwarding state. The Bridge Forward Delay is set by the Root
bridge in the network. You can edit the Bridge Forward Delay value
but, unless the FDMMIM is the Root bridge, the new value has no
effect. The new value becomes effective only when the FDMMIM
becomes the Root. (Default = 15 seconds. The allowable range is 4 to
30 seconds.)
Time Since Topology Change indicates the elapsed time (in
seconds) since the last change to the bridge Topology Change Flag.