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Chapter 11
Configuring VLANs
Configuring a Trunk Port
Beginning in privileged EXEC mode, follow these steps to configure a port as an IEEE 802.1Q
trunk port:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
no shutdown
Step 4
switchport mode trunk
Step 5
switchport access vlan vlan-id
Step 6
switchport trunk native vlan vlan-id
Step 7
end
Step 8
show interfaces interface-id switchport Display the switchport configuration of the interface in the Administrative
Step 9
show interfaces interface-id trunk
Step 10
copy running-config startup-config
To return an interface to its default configuration, use the default interface interface-id interface
configuration command. To reset all trunking characteristics of a trunking interface to the defaults, use
the no switchport trunk interface configuration command. To disable trunking, use the switchport
mode access interface configuration command to configure the port as a static-access port.
This example shows how to configure a port as an IEEE 802.1Q trunk with VLAN 33 as the native
VLAN:
Switch# configure terminal
Enter configuration commands, one per line.
Switch(config)# interface fastethernet0/2
Switch(config-if)# switchport mode trunk
Switch(config-if)# switchport trunk native vlan 33
Switch(config-if)# end
Defining the Allowed VLANs on a Trunk
By default, a trunk port sends traffic to and receives traffic from all VLANs. All VLAN IDs, 1 to 4094,
are allowed on each trunk. However, you can remove VLANs from the allowed list, preventing traffic
from those VLANs from passing over the trunk. To restrict the traffic a trunk carries, use the switchport
trunk allowed vlan remove vlan-list interface configuration command to remove specific VLANs from
the allowed list.
78-17058-01
Purpose
Enter global configuration mode.
Specify the port to be configured for trunking, and enter interface
configuration mode.
Enable the port, if necessary. By default, UNIs are disabled, and NNIs are
enabled.
Configure the interface as a Layer 2 trunk.
(Optional) Specify the default VLAN, which is used if the interface stops
trunking.
Specify the native VLAN for IEEE 802.1Q trunks.
Return to privileged EXEC mode.
Mode field of the display.
Display the trunk configuration of the interface.
(Optional) Save your entries in the configuration file.
End with CNTL/Z.
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Configuring VLAN Trunks
11-17
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