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| Table 23 Spanning Tree Protocol: Configuration (continued) | |
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| LABEL | DESCRIPTION |
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| Bridge Priority | Bridge priority is used in determining the root switch, root port and designated port. |
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| The switch with the highest priority (lowest numeric value) becomes the STP root |
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| switch. If all switches have the same priority, the switch with the lowest MAC |
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| address will then become the root switch. Select a value from the |
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| box. |
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| The lower the numeric value you assign, the higher the priority for this bridge. |
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| Bridge Priority determines the root bridge, which in turn determines Hello Time, |
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| Max Age and Forwarding Delay. |
| Hello Time | This is the time interval in seconds between BPDU (Bridge Protocol Data Units) |
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| configuration message generations by the root switch. The allowed range is 1 to 10 |
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| seconds. |
| Max Age | This is the maximum time (in seconds) a switch can wait without receiving a BPDU |
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| before attempting to reconfigure. All switch ports (except for designated ports) |
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| should receive BPDUs at regular intervals. Any port that ages out STP information |
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| (provided in the last BPDU) becomes the designated port for the attached LAN. If it |
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| is a root port, a new root port is selected from among the switch ports attached to |
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| the network. The allowed range is 6 to 40 seconds. |
| Forwarding Delay | This is the maximum time (in seconds) a switch will wait before changing states. |
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| This delay is required because every switch must receive information about |
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| topology changes before it starts to forward frames. In addition, each port needs |
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| time to listen for conflicting information that would make it return to a blocking state; |
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| otherwise, temporary data loops might result. The allowed range is 4 to 30 |
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| seconds. |
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| As a general rule: |
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| Note: 2 * (Forward Delay - 1) >= Max Age >= 2 * (Hello Time + 1) |
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| Port | This field displays the port number. |
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| Active | Select this check box to activate STP on this port. |
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| Priority | Configure the priority for each port here. |
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| Priority decides which port should be disabled when more than one port forms a |
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| loop in a switch. Ports with a higher priority numeric value are disabled first. The |
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| allowed range is between 0 and 255 and the default value is 128. |
| Path Cost | Path cost is the cost of transmitting a frame on to a LAN through that port. It is |
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| assigned according to the speed of the bridge. The slower the media, the higher |
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| the cost - see Table 20 on page 87 for more information. |
| Apply | Click Apply to save your changes back to the switch. |
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| Cancel | Click Cancel to begin configuring this screen afresh. |
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Chapter 11 Spanning Tree Protocol | 91 |