Cabletron Systems 7C04-R, 7C03 manual Designated Root, Num. Topology Chgs, Forward Delay, Max Age

Using the 7C0x SmartSwitch Bridge View

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CAUTION

All bridges in a network must use the same Spanning Tree version. Mixing Spanning Tree Algorithm protocols will cause an unstable network.

Designated Root

This value represents the bridge that is the current Root Bridge as determined by the STA. The Designated Root value consists of the configurable portion of the bridge ID (i.e., the first two octets of the eight-octet-long bridge ID) and the root bridge device’s MAC address (the last six octets of the bridge ID). This value is used as the Root Identifier parameter in all configuration BPDUs originated from this node.

Num. Topology Chgs.

Indicates the number of times the bridge’s Topology Change flag has been changed since the bridge was powered up or initialized. The Topology Change flag increments each time any of the network’s bridges enters or leaves the network or when the Root Bridge ID changes.

The values for the following three fields—Forward Delay, Max Age, and Hello Time—represent 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 values—Root Forward Delay, Root Max Age, Root Hello Time—that 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 Ageing 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 bridge’s BPDU ageing timer, in seconds. The ageing timer defines the maximum number of seconds 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 If the timer expires before a new Configuration BPDU is received, it indicates that the former Root is no longer active.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 Root Bridge determines the Max Age. The range for this field is from 6 to 40 seconds, with a default value of 20 seconds.

6-22 The Spanning Tree Protocol Window