13-27
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter13 Configuring VLANs
Configuring VLAN Trunks
In Figure 13-4, 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.
Figure13-4 Load-Sharing Trunks with Traffic Distributed by Path Cost
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure 13-4:
90573
Switch A
Switch B
Trunk port 1
VLANs 24 (path cost 30)
VLANs 810 (path cost 19)
Trunk port 2
VLANs 810 (path cost 30)
VLANs 24 (path cost 19)
Command Purpose
Step1 configure terminal Enter global configuration mode on SwitchA.
Step2 interface interface-id_1 Define the interface to be configured as a trunk, and enter interface
configuration mode.
Step3 switchport trunk encapsulation
{isl | dot1q | negotiate}
Configure the port to support ISL or IEEE 802.1Q encapsulation. You
must configure each end of the link with the same encapsulation type.
Step4 switchport mode trunk Configure the port as a trunk port. The trunk defaults to ISL trunking.
Step5 exit Return to global configuration mode.
Step6 Repeat Steps 2 through 5 on a second interface in the Switch A stack.
Step7 end Return to privileged EXEC mode.
Step8 show running-config Verify your entries. In the display, make sure that the interfaces are
configured as trunk ports.
Step9 show vlan When the trunk links come up, Switch A receives the VTP information
from the other switches. Verify that Switch A has learned the VLAN
configuration.
Step10 configure terminal Enter global configuration mode.
Step11 interface interface-id_1 Define the interface on which to set the STP cost, and enter interface
configuration mode.
Step12 spanning-tree vlan 2-4 cost 30 Set the spanning-tree path cost to 30 for VLANs 2 through 4.
Step13 end Return to global configuration mode.