You may use the following method to configure a Cisco Catalyst3560 switch port as a trunk. In this example we will use the FastEthernet 0/24 port.

Begin by entering global configuration mode and specifying the port, FastEthernet 0/24, that will be configured as a trunk port.

Cisco - Configure Cisco 3560 Switch Trunk Port - 00

Next, we must specify the version of trunking we will implement. In this example we will implement IEEE 802.1q trunking which is specified by the switchport trunk encapsulation dot1q command.

Cisco - Configure Cisco 3560 Switch Trunk Port - 01

Next, we enable the trunk with the switchport mode trunk command. Note that this command will automatically negotiates to convert the link on the other end to a trunk link.

Cisco - Configure Cisco 3560 Switch Trunk Port - 02

Lastly, you may verify the trunk port with the show interface trunk command.

Cisco - Configure Cisco 3560 Switch Trunk Port - 03

Enjoy!