Spanning Tree Algorithm Configuration
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•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.
• Range –
- Ethernet: 200,000-20,000,000
- Fast Ethernet: 20,000-2,000,000
- Gigabit Ethernet: 2,000-200,000
• 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
Web – Click Spanning Tree, MSTP, Port Configuration or Trunk Configuration. Enter
the priority and path cost for an interface, and click Apply.
Figure 3-60. MSTP Port Configuration
CLI – This example sets the MSTP attributes for port 4.
Console(config)#interface ethernet 1/4 4-125
Console(config-if)#spanning-tree mst port-priority 0 4-168
Console(config-if)#spanning-tree mst cost 50 4-167
Console(config-if)