Dimension
Chapter 10
Spanning Tree Protocol
This chapter describes the basics and configuration of STP.
10.1 Introduction
Spanning Tree Protocol) is a standardized method (IEEE 802.1D) that eliminates loops in a network by disabling some ports and allowing other ports to forward traffic based on the parameters you configured. STP ensures that there is only one path between a specific source and destination so packets will not travel in loops.
STP provides path redundancy while preventing undesirable loops in the network. STP detects and breaks network loops and provides backup links between switches, bridges or routers. It allows a device to interact with other
The root bridge is the base of the spanning tree; it is the bridge with the lowest identifier value (MAC address). Path cost is the cost of transmitting a frame onto a LAN through that port. It is assigned according to the speed of the link to which a port is attached. The slower the media, the higher the cost. Refer to the following table for the recommended path cost (in the allowed range between 1 and 65535) for each link speed.
Table 10-1 Recommended Path Cost
LINK SPEED | RECOMMENDED VALUE | RECOMMENDED RANGE |
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4Mbps | 250 | 100 to 1000 |
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10Mbps | 100 | 50 to 600 |
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16Mbps | 62 | 40 to 400 |
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100Mbps | 19 | 10 to 60 |
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1Gbps | 4 | 3 to 10 |
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10Gbps | 2 | 1 to 5 |
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On each bridge, the root port is the port through which a bridge communicates with the root. It is the port on this switch with the lowest path cost to the root (the root path cost). If there is no root port, then this switch has been accepted as the root bridge of the spanning tree network.
Spanning Tree Protocol |