VLAN

encapsulation dot1q run in a router to split an interface using the 802.1Q trunking protocol switchport mode access configure the interface to operate in access mode switchport access vlan
Assign the port/range of ports into access ports. A port in access mode can have only one

VLAN configured on the interface which can carry traffic for only one VLAN

switchport mode trunk configure the interface to operate in trunking mode neighbor distribute-list out Filter routes to neighbor using ACL interface tunnel mode ipv6
Note: In Cisco switches, port numbers 0/x are reserved for the switch's internal use and management, and they cannot be used as regular switch ports or trunk ports for VLAN traffic. And the ones we use Cisco 3700 series routers' 0/x interfaces are mainly for Layer 3 operations like routing, so they cannot act as Layer 2 to support switchport mode commands. It might also be necessary to reboot the device after configuration for changes to take effect.