Simple Stp Configuration - Lenovo RackSwitch G8264CS Application Manual

Port Path Cost

Simple STP Configuration

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G8264CS Application Guide for ENOS 8.4
The port path cost assigns lower values to high‐bandwidth ports, such as 10
Gigabit Ethernet, to encourage their use. 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 speed.
Use the following command to modify the port path cost:
RS 8264CS(config)# interface port <port number>
RS 8264CS(config-if)# spanning-tree stp <STG number or range> path-cost <path
cost value>
RS 8264CS(config-if)# exit
The port path cost can be a value from 1 to 200000000. Specify 0 for automatic path
cost.
Figure 11 depicts a simple topology using a switch‐to‐switch link between two
G8264CS 1 and 2.
Figure 11. Spanning Tree Blocking a Switch‐to‐Switch Link
Enterprise
Routing
Switches
Switch 1
Server Server
To prevent a network loop among the switches, STP must block one of the links
between them. In this case, it is desired that STP block the link between the Lenovo
switches, and not one of the G8264CS uplinks or the Enterprise switch LAG.
During operation, if one G8264CS experiences an uplink failure, STP will activate
the Lenovo switch‐to‐switch link so that server traffic on the affected G8264CS may
pass through to the active uplink on the other G8264CS, as shown in Figure
x
STP
Blocks Link
Server Server
Switch 2
12.