Cabletron Systems CSX400 - Manual (Page 50)

CSX Bridge View
3-30 The Spanning Tree Protocol Window
the Root IdentiÞer parameter in all conÞguration BPDUs originated from this
node.
Num. Topology Chgs.
Indicates the number of times the bridgeÕs Topology Change ßag has been
changed since the bridge was powered up or initialized. The Topology Change
ßag increments each time any of the networkÕs bridges enters or leaves the
network or when the Root Bridge ID changes.
The values for the following three ÞeldsÑForward Delay, Max Age, and Hello
TimeÑrepresent the values that are currently being used by all bridges, as
dictated by the Root bridge. In the Spanning Tree Protocol window, you can view
and set the valuesÑRoot Forward Delay, Root Max Age, Root Hello TimeÑthat
will be in effect when the bridge for which you are setting the parameters
becomes the Root Bridge.
Forward Delay
The length of time, in seconds, that controls how long a bridge port remains in
each state (Forwarding, Learning, Listening, etc.) when moving toward the
Forwarding state. During a topology change, the Forward Delay is also used as
the Filtering Database Aging Time, which ensures that the Filtering Database will
contain current topology information. The Root Bridge sets the Forward Delay.
Max Age
The current setting for the bridgeÕs BPDU aging timer, in seconds. The aging timer
deÞnes the maximum number of seconds that a ConÞguration BPDU is retained
by the bridge before it is discarded. During normal operation, each bridge in the
network receives a new ConÞguration BPDU before the aging timer expires. If the
timer expires before a new ConÞguration 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former Root is no longer active.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 Root Bridge determines the Max Age. The
range for this Þeld is from 6 to 40 seconds, with a default value of 20 seconds.
Hello Time
Indicates, in seconds, the length of time the Root Bridge, or bridge attempting to
become the Root, waits before resending a ConÞguration BPDU. The Root Bridge
determines the Hello Time.
Priority
The Spanning Tree Algorithm assigns each bridge a unique identiÞer, which is
derived from the individual portÕs MAC address and its priority as determined
by the Spanning Tree Algorithm or your setting. The bridge with the lowest value
of bridge identiÞer is selected as the Root. A lower priority number indicates a
higher priority; a higher priority enhances a bridgeÕs chance of being selected as
the Root.
Acceptable values range from 0-FFFF and can be edited to change the network
topology, if needed. The default is 8000.