Configuring an TRUNK port on a Cisco switch

A Trunk port is a port that has been configured to carry multiple VLAN Traffic.

There are currently 2 supported methods

• Inter-Switch Link (ISL) - Cisco proprietary trunk protocol
• Dot1q - IEEE Standard 802.1q

Below is the minimum configuration required for configuring a trunk port. Please note, the same would need to be done on the switch on the other end of the cable as well :

SW1>enable

SW1#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

SW1(config)#interface fa0/10

SW1(config-if)#switchport trunk encapsulation dot1q

SW1(config-if)#switchport mode trunk

SW1(config-if)#no shut         

SW1(config-if)#end

SW1#

Verify your trunk link configuration:

SW1#show interface FastEthernet0/10 trunk

Port      Mode         Encapsulation  Status        Native vlan

Fa0/10    on           802.1q         trunking      1

Port      Vlans allowed on trunk

Fa0/10    1-4094

Port      Vlans allowed and active in management domain

Fa0/10    1,10

Port      Vlans in spanning tree forwarding state and not pruned

Fa0/10    1

SW1#