Trunk port configuration - Cisco
Technology: Switching
Area: VLAN
Vendor: Cisco
Software: 12.X , 15.X, IP Base, IP Services, LAN Base, LAN Light
Platform: Catalyst 2960-X, Catalyst 3560

Trunk port configuration example to carry the different VLAN tags between two devices on the same physical link. Vendor agnostic technology (IEEE 802.1Q)

Switch(config)# interface GigabitEthernet 0/0/10
Switch(config-if)# switchport trunk encapsulation dot1q
Switch(config-if)# switchport mode trunk

By default this configuration allows all VLANs to be transmitted over the trunk link. To restrict the link to carry only specified VLANs use the allowed vlan command

Switch(config)# interface GigabitEthernet 0/0/10
Switch(config-if)# switchport trunk allowed vlan 10,20,30,40

To verify how the trunk port is configured you can issue few show commands:

Switch# show run interface GigabitEthernet 0/0/10
Switch# show interface trunk