In this post , we share step by step tested and working command line procedures to enable Trunk/ VLAN tagged ports on a Cisco switch and cover the following topics- How to create and enable a Trunk port
- How to assign VLANs to a Trunk port
- How to View the trunk properties
- How to Disable a Trunk port.
Switch1# config terminal
Select the interface port which has to be set as trunk port
Switch1(config)#interface
f1/0/1
If this trunk carries traffic of more than one VLAN enable 802.1q support
Switch1(config-if)#switchport
trunk encapsulation dot1q
Set the port mode to trunk
Switch1(config-if)#switchport
mode trunk
Activate the trunk port
Switch1(config-if)#no
shut
Switch1(config-if)#^Z
By default when 802.1q VLAN tagging is enabled , all the VLANs will be automatically assigned to the trunk port. However specific VLANs may be allowed / disallowed using the below commands.
Switch1# config t
Switch1(config)#interface f3/0/33
To remove VLAN 200 from the trunk.
Switch1(config-if)# switchport trunk allowed vlan remove 200
Switch1(config-if)#^Z
To allow VLAN 100 on the trunk port
Switch1(config-if)#switchport trunk allowed vlan add 100
Switch1(config-if)#
To allow all VLANs expect VLAN 300 on trunk port
Switch1(config-if)#
Switch1(config-if)#switchport trunk allowed vlan except 200
To allow all VLANs traffic on the trunk port
Switch1(config-if)#
Switch1(config-if)#switchport trunk allowed vlan all
Switch1(config-if)#
How to view the trunk port properties
Switch1 #
show int f1/0/1 trunk
Port Mode Encapsulation Status
Native vlan
Fa1/0/1 on 802.1q trunking 1
Port Vlans allowed on trunk
Fa1/0/1 1-4094
Port Vlans allowed and active in management domain
Fa1/0/1 1,100,200 (VLANs will be displayed only
when cable is connected to port)
Port Vlans in spanning tree forwarding state
and not pruned
Fa1/0/1 none
Switch1# show interfaces trunk
Port Mode Encapsulation Status Native vlan
Fa1/0/1 on 802.1q trunking 1
Port Vlans allowed on trunk
Fa1/0/1 1-4094
Port Vlans allowed and active in management domain
Fa1/0/1 1,100,200
Port Vlans in spanning tree forwarding state and not pruned
Fa1/0/1 1,100,200
Switch1 # show
interfaces f1/0/1 switchport
Name: Fa1/0/1
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association:
none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN:
none
Administrative private-vlan trunk Native VLAN
tagging: enabled
Administrative private-vlan trunk
encapsulation: dot1q
Administrative private-vlan trunk normal
VLANs: none
Administrative private-vlan trunk
associations: none
Administrative private-vlan trunk mappings:
none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
How to disable a trunk port
Switch1(config)#interface
f1/0/1
Switch1(config-if)#no switchport
trunk encapsulation dot1q
Switch1(config-if)#no switchport
mode trunk
Switch1(config-if)#switchport mode access
Hope this helps some Cisco switch learning beginners.