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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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Chapter 11 Configuring VLANs
Configuring VLAN Trunks
Follow the same steps on Switch B to configure the trunk port for Trunk 1 with a spanning-tree port
priority of 16 for VLANs 8 through 10, and the configure trunk port for Trunk 2 with a spanning-tree
port priority of 16 for VLANs 3 through 6.
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, blocking different ports for different VLANs.
The VLANs keep the traffic separate and maintain redundancy in the event of a lost link.
In Figure 11-4, Trunk ports 1 and 2 are configured as 100Base-T ports. These VLAN path costs are
assigned:
• VLANs 2 through 4 are assigned a path cost of 30 on Trunk port 1.
• VLANs 8 through 10 retain the default 100Base-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 100Base-T path cost on Trunk port 2 of 19.
Figure 11-4 Load-Sharing Trunks with Traffic Distributed by Path Cost
Step 17
interface gigabitethernet 0/2 Define the interface to be configured as the Trunk 2 interface, and
enter interface configuration mode.
Step 18
port-type nni Configure the interface as an NNI.
Step 19
switchport mode trunk Configure the port as a trunk port.
Step 20
spanning-tree vlan 3-6 port-priority 16 Assign the port priority of 16 for VLANs 3 through 6 on Trunk 2.
Step 21
end Return to privileged EXEC mode.
Step 22
show interfaces gigabitethernet 0/2
switchport
Verify the port configuration.
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
90573
Switch A
Switch B
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)