Switchport Trunk Encapsulation dot1q Command on CISCO Router/Switch

Command

Switchport Trunk Encapsulation dot1q

Use

Enables dot1q trunking encapsulation on the interface.

Syntax

Switch(config-if)#switchport trunk encapsulation dot1q

Example

First, here is the trunking information for SW3. Note fa0/19, which is set to ISL.

SW3(config-if)#do show int trunkPort Mode Encapsulation Status Native vlan
Fa0/19 auto isl trunking 1
Fa0/20 auto n-802.1q trunking 1
Fa0/21 auto n-802.1q trunking 1
Fa0/22 auto n-802.1q trunking 1
Port Vlans allowed on trunk
Fa0/19 1-4094
Fa0/20 1-4094
Fa0/21 1-4094
Fa0/22 1-4094

Port Vlans allowed and active in management domain
Fa0/19 1,10-20,55,99,555
Fa0/20 1,10-20,55,99,555
Fa0/21 1,10-20,55,99,555
Fa0/22 1,10-20,55,99,555

Port Vlans in spanning tree forwarding state and not pruned
Fa0/19 none
Fa0/20 none
Fa0/21 1,10-11
Fa0/22 none
SW3(config-if)#

Next, dot1q trunking is enabled on fa0/2 on SW3.

SW3(config)#int fa0/2
SW3(config-if)#switchport trunk encapsulation dot1q

Here is the trunking information after making the changes.

SW3(config-if)#do show int trunkPort Mode Encapsulation Status Native vlan
Fa0/19 auto 802.1q trunking 1
Fa0/20 auto n-802.1q trunking 1
Fa0/21 auto n-802.1q trunking 1
Fa0/22 auto n-802.1q trunking 1
Port Vlans allowed on trunk
Fa0/19 1-4094
Fa0/20 1-4094
Fa0/21 1-4094
Fa0/22 1-4094

Port Vlans allowed and active in management domain
Fa0/19 1,10-20,55,99,555
Fa0/20
03:12:24: %LINEPROTO-5-UPDOWN: Line1,10-20,55,99,555
Fa0/21 1,10-20,55,99,555
Fa0/22 1,10-20,55,99,555

Port Vlans in spanning tree forwarding state and not pruned
Fa0/19 none
Fa0/20 none
Fa0/21 1,10-11
protocol on Interface FastEthernet0/19, changed state to up

Port Vlans in spanning tree forwarding state and not pruned
Fa0/22 none

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