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 | Spanning | |
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| Field | Description | 
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| Bridge Maximum | Configurable field; the maximum permissible age, in | |
| Age | seconds, provided by the current root bridge for | |
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 | Spanning Tree configuration information to remain | |
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 | active on the selected bridge. | |
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 | When the  | |
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 | received any BPDUs, it discards the current Spanning | |
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 | Tree information and initiates a new round of Span- | |
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 | ning Tree configuration. | |
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 | The recommended IEEE 802.1d time is 20s (twenty | |
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 | seconds). | |
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| Bridge Hello Time | Configurable field; the amount of time, in seconds, | |
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 | provided by the current root bridge between trans- | |
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 | missions of configuration BPDUs. This timer works | |
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 | with the Spanning Tree Hold Time, which should be | |
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 | greater than the Hello Time. | |
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 | If it is smaller, the Spanning Tree algorithm responds | |
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 | more quickly to configuration changes, resulting in | |
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 | increased network traffic. | |
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 | The recommended IEEE 802.1d time is 2s (two sec- | |
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 | onds). | |
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| Bridge Forward | Configurable field; the delay time, in seconds, pro- | |
| Delay | vided by the current root bridge before a bridge starts | |
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 | forwarding data packets. | |
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 | The recommended IEEE 802.1d time is 15s (15 sec- | |
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 | onds). | |
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| Time Since Topol- | ||
| ogy Change | topology was changed. | |
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| Number Topology | ||
| Changes | changes that have occurred. | |
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