Port Path Cost; Simple Stp Configuration - Lenovo CN4093 Application Manual

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Port Path Cost

CN4093 Application Guide for N/OS 8.3

The port path cost assigns lower values to high-bandwidth ports, such as 10

Gigabit Ethernet, to encourage their use. The cost of a port also depends on

whether the port operates at full-duplex (lower cost) or half-duplex (higher cost).

For example, if a 100-Mbps (Fast Ethernet) link has a "cost" of 10 in half-duplex

mode, it will have a cost of 5 in full-duplex mode. The objective is to use the fastest

links so that the route with the lowest cost is chosen. A value of 0 (the default)

indicates that the default cost will be computed for an auto-negotiated link or LAG

Use the following command to modify the port path cost:

CN 4093(config)# interface port <port alias or number>

CN 4093(config-if)# spanning-tree stp <1-128> path-cost <path cost value>

CN 4093(config-if)# exit

The port path cost can be a value from 1 to 200000000. Specify 0 for automatic path

depicts a simple topology using a switch-to-switch link between two

switches (via either external ports or internal Inter-Switch Links).

Figure 11. Spanning Tree Blocking a Switch-to-Switch Link