Specifications

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Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR
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Chapter 7 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, blocking different ports for different VLANs.
The VLANs keep the traffic separate and maintain redundancy in the event of a lost link.
In Figure 7-3, 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 7-3 Load-Sharing Trunks with Traffic Distributed by Path Cost
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure 7-3:
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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)
Command Purpose
Step 1
configure terminal Enter global configuration mode on Switch A.
Step 2
interface fastethernet0/1 Define the interface to be configured as Trunk port 1, and enter interface
configuration mode.
Step 3
switchport mode trunk Configure the port as a trunk port.
Step 4
exit Return to global configuration mode.
Step 5
interface fastethernet0/2 Define the interface to be configured as Trunk port 2, and enter interface
configuration mode.
Step 6
switchport mode trunk Configure the port as a trunk port.
Step 7
end Return to privileged EXEC mode.
Step 8
show running-config Verify your entries. In the display, make sure that the interfaces
configured in Steps 2 and 7 are configured as trunk ports.
Step 9
show vlan Verify that VLANs 2 through 4 and 8 through 10 are configured on
Switch A. If not, create these VLANs.
Step 10
configure terminal Enter global configuration mode.
Step 11
interface fastethernet0/1 Enter interface configuration mode for Trunk port 2.
Step 12
spanning-tree vlan 2-4 cost 30 Set the spanning-tree path cost to 30 for VLANs 2 through 4.