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Cisco ME 3800X and 3600X Switch Software Configuration Guide
OL-23400-01
Chapter 10 Configuring VLANs
Configuring VLAN Trunks
Figure 10-2 Load Sharing by Using STP Port Priorities
Beginning in privileged EXEC mode on Switch A, follow these steps to configure the network shown in
Figure 10-2. Note that you can use any interface numbers; those shown are examples only.
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.
93370
Switch A
Switch B
Trunk 2
VLANs 3 – 6 (priority 16)
VLANs 8 – 10 (priority 128)
Trunk 1
VLANs 8 – 10 (priority 16)
VLANs 3 – 6 (priority 128)
Command Purpose
Step 7
show vlan Verify that the referenced VLANs exist on Switch A. If not, create the
VLANs by entering the VLAN IDs.
Step 8
configure terminal Enter global configuration mode.
Step 9
interface gigabitethernet 0/1 Define the interface to be configured as the Trunk 1 interface, and
enter interface configuration mode.
Step 10
switchport mode trunk Configure the port as a trunk port.
Step 11
spanning-tree vlan 8-10 port-priority 16 Assign the port priority of 16 for VLANs 8 through 10 on Trunk 1.
Step 12
end Return to privileged EXEC mode.
Step 13
show interfaces gigabitethernet 0/1
switchport
Verify the port configuration.
Step 14
configure terminal Enter global configuration mode.
Step 15
interface gigabitethernet 0/2 Define the interface to be configured as the Trunk 2 interface, and
enter interface configuration mode.
Step 16
switchport mode trunk Configure the port as a trunk port.
Step 17
spanning-tree vlan 3-6 port-priority 16 Assign the port priority of 16 for VLANs 3 through 6 on Trunk 2.
Step 18
end Return to privileged EXEC mode.
Step 19
show interfaces gigabitethernet 0/2
switchport
Verify the port configuration.
Step 20
show running-config Verify your entries.
Step 21
copy running-config startup-config (Optional) Save your entries in the configuration file.
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