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Cisco Systems Intelligent Gigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
24R9746
Chapter 12 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 Figure 12-4, Trunk ports 1 and 2 are 1000BASE-T ports. 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.
Figure 12-4 Load-Sharing Trunks with Traffic Distributed by Path Cost
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure 12-4:
Step 19
exit Return to global configuration mode.
Step 20
interface gigabitethernet0/18 Enter interface configuration mode, and define the interface to set the
STP port priority.
Step 21
spanning-tree vlan 3-6 port-priority 16 Assign the port priority of 16 for VLANs 3 through 6.
Step 22
end Return to privileged EXEC mode.
Step 23
show running-config Verify your entries.
Step 24
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
Step 1
configure terminal Enter global configuration mode on Switch A.
Step 2
interface gigabitethernet0/17 Enter interface configuration mode, and define Gigabit Ethernet
port 0/17 as the interface to be configured as a trunk.
Step 3
switchport mode trunk Configure the port as a trunk port.