Spanning Tree Algorithm Configuration 3

Protocol is detecting network loops. Where more than one port is assigned the highest priority, the port with lowest numeric identifier will be enabled.

•Default: 128

•Range: 0-240, in steps of 16

•Admin MST Path Cost – This parameter is used by the MSTP to determine the best path between devices. Therefore, lower values should be assigned to ports attached to faster media, and higher values assigned to ports with slower media. (Path cost takes precedence over port priority.) Note that when the Path Cost Method is set to short (page 3-63), the maximum path cost is 65,535.

By default, the system automatically detects the speed and duplex mode used on each port, and configures the path cost according to the values shown below. Path cost “0” is used to indicate auto-configuration mode.

•Range –

-Ethernet: 200,000-20,000,000

-Fast Ethernet: 20,000-2,000,000

-Gigabit Ethernet: 2,000-200,000

-10 Gigabit Ethernet: 200-20,000

•Default –

-Ethernet – Half duplex: 2,000,000; full duplex: 1,000,000; trunk: 500,000

-Fast Ethernet – Half duplex: 200,000; full duplex: 100,000; trunk: 50,000

-Gigabit Ethernet – Full duplex: 10,000; trunk: 5,000

-10 Gigabit Ethernet – Full duplex: 1000; trunk: 500

Web – Click Spanning Tree, MSTP, Port Configuration or Trunk Configuration. Enter the priority and path cost for an interface, and click Apply.

Figure 3-73 MSTP Port Configuration

CLI – This example sets the MSTP attributes for port 4.

Console(config)#interface ethernet 1/4

 

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Console(config-if)#spanning-tree mst 1

port-priority 0

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Console(config-if)#spanning-tree mst 1

cost 50

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Console(config-if)

 

 

 

 

 

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