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Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBMBladeCenter, Software Configuration Guide
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Chapter12 Configuring VLANs
Configuring VLAN Trunks
Load Sharing Using STP Path Cost
You can configure parallel trunks to share VLAN traffic by setting different path costs on a trunk and
associating the path costs with different sets of VLANs. The VLANs keep the traffic separate. Because
no loops exist, STP does not disable the ports, and redundancy is maintained in the event of a lost link.
In Figure12-4, Trunk ports 1 and 2 are 1000BASE-T po rts. The path costs for the VLANs are assigned
as follows:
•VLANs 2 through 4 are assigned a path cost of 30 on Trunk port 1 .
•VLANs 8 through 10 retain the default 1000BASE-T path cost on Trunk port 1 of 19.
•VLANs 8 through 10 are assigned a path cost of 30 on Trunk port 2.
•VLANs 2 through 4 retain the default 1000BASE-T path cost on Trunk port 2 of 19.
Figure12-4 Load-Sharing Trunks with Traffic Distributed by Path Cost
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure12-4:
Step19 exit Return to global configuration mode.
Step20 interface gigabitethernet0/18 Enter interface configuration mode, and define the interface to set the
STP port priority.
Step21 spanning-tree vlan 3-6 port-priority 16 Assign the port priority of 16 for VLANs 3 through 6.
Step22 end Return to privileged EXEC mode.
Step23 show running-config Verify your entries.
Step24 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
92414
Switch 1
BladeCenter
Trunk port 1
VLANs 2 – 4 (path cost 30)
VLANs 8 – 10 (path cost 19)
Trunk port 2
VLANs 8 – 10 (path cost 30)
VLANs 2 – 4 (path cost 19)
Command Purpose
Step1 configure terminal Enter global configuration mode on Switch A.
Step2 interface gigabitethernet0/17 Enter interface configuration mode, and define Gigabit Ethernet
port 0/17 as the interface to be configured as a trunk.
Step3 switchport mode trunk Configure the port as a trunk port.