Final answer:
All VLANs, including the native VLAN, are allowed on trunk ports by default. VLAN tagging is used to manage traffic across VLANs, and specific VLANs can be included or excluded through manual configuration for security and network efficiency.
Step-by-step explanation:
By default, traffic from all VLANs, including the native VLAN (which is typically VLAN 1), are allowed on trunk ports on a switch. A trunk port on a network switch is used to pass traffic between switches and routers for multiple VLANs. It is a common configuration on managed switches in enterprise networks. Network administrators often configure VLAN tagging on trunk ports to ensure that traffic is properly segregated between VLANs as it traverses the network. If specific VLANs need to be excluded from a trunk link, this must be configured manually through the switch's management software or command-line interface.
However, it is important for security and network design reasons to control which VLANs are permitted on a trunk port. This is usually done using VLAN pruning or by explicitly setting the allowed VLANs on the trunk. Only the necessary VLANs should be allowed on trunk links to reduce the risk of VLAN hopping attacks and to minimize unnecessary traffic.