Installation and Getting Started Guide
STP Parameters and Defaults
Table 5.1 lists the default STP bridge parameters. The bridge parameters affect the entire VLAN (or the entire device, if the only
Table 5.1: Default STP Bridge Parameters
Parameter | Description | Default and Valid Values |
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Forward Delay | The period of time a bridge will wait (the listen and learn | 15 seconds |
| period) before beginning to forward data packets. | Possible values: 4 – 30 |
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| seconds |
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Maximum Age | The interval a bridge will wait for a hello packet from the | 20 seconds |
| root bridge before initiating a topology change. | Possible values: 6 – 40 |
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| seconds |
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Hello Time | The interval of time between each configuration BPDU | 2 seconds |
| sent by the root bridge. | Possible values: 1 – 10 |
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| seconds |
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Priority | A parameter used to identify the root bridge in a | 32768 |
| spanning tree (instance of STP). The bridge with the | Possible values: 0 – 65535 |
| lowest value has the highest priority and is the root. | |
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| A higher numerical value means a lower priority; thus, |
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| the highest priority is 0. |
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Table 5.2 lists the default STP port parameters. The port parameters affect individual ports and are separately configurable on each port.
Table 5.2: Default STP Port Parameters
Parameter | Description | Default and Valid Values |
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Priority | The preference that STP gives this port relative to other | 128 |
| ports for forwarding traffic out of the spanning tree. | Possible values: 0 – 255 |
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| A higher numerical value means a lower priority; thus, |
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| the highest priority is 0. |
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Path Cost | The cost of using the port to reach the root bridge. When | 10 Mbps – 100 |
| selecting among multiple links to the root bridge, STP | 100 Mbps – 19 |
| chooses the link with the lowest path cost and blocks the | |
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| |
| other paths. Each port type has its own default STP path | Gigabit – 4 |
| cost. | Possible values are 0 – |
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| 65535 |
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