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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 12 Configuring VLANs
Configuring VLAN Trunks
In Figure 12-4, Trunk ports 1 and 2 are 100BASE-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 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 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:
16591
Switch 1
Switch 2
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 1.
Step 2
interface fastethernet 0/1 Enter interface configuration mode, and define Fast Ethernet port 0/1 as
the interface to be configured as a trunk.
Step 3
switchport trunk encapsulation
{isl | dot1q | negotiate}
Configure the port to support ISL or 802.1Q encapsulation.
You must configure each end of the link with the same encapsulation
type.
Step 4
switchport mode trunk Configure the port as a trunk port.
The trunk defaults to ISL trunking.
Step 5
exit Return to global configuration mode.
Step 6
Repeat Steps 2 through 4 on Switch 1 interface Fast Ethernet 0/2.
Step 7
end Return to privileged EXEC mode.
Step 8
show running-config Verify your entries.
In the display, make sure that interfaces Fast Ethernet 0/1 and Fast
Ethernet 0/2 are configured as trunk ports.
Step 9
show vlan When the trunk links come up, Switch 1 receives the VTP information
from the other switches. Verify that Switch 1 has learned the VLAN
configuration.
Step 10
configure terminal Enter global configuration mode.
Step 11
interface fastethernet 0/1 Enter interface configuration mode, and define Fast Ethernet port 0/1 as
the interface to set the STP cost.
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