Port Path Cost
Simple STP Configuration
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G8264 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 G8264(config)# interface port <port number>
RS G8264(configif)# spanningtree stp <STG number or range> pathcost <path cost
value>
RS G8264(configif)# 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
G8264 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 G8264 uplinks or the Enterprise switch LAG.
During operation, if one G8264 experiences an uplink failure, STP will activate the
Lenovo switch‐to‐switch link so that server traffic on the affected G8264 may pass
through to the active uplink on the other G8264, as shown in Figure
x
STP
Blocks Link
Server
Server
Switch 2
12.