Which of the following statements about trunks is true?

The statement that trunks carry traffic for multiple VLANs only if those VLANs exist on the switch and are allowed on the trunked interfaces is accurate because trunks are designed to handle traffic from multiple VLANs simultaneously. When a trunk link is established between switches or network devices, it allows the passage of traffic from several VLANs over a single physical link, as long as the VLANs are configured on the devices involved.

Trunks work by tagging frames with a VLAN identifier that tells the receiving device which VLAN the traffic belongs to. For this to function correctly, it is essential that the VLANs are already created on the participating switches. Additionally, the trunk configuration must specify which VLANs are allowed to traverse that trunk. For instance, a switch may have several VLANs configured, but if a trunk is not set up to permit certain VLANs, traffic from those VLANs cannot flow through that trunk, effectively filtering it out.

This design is critical in maintaining proper network segmentation and ensuring that only intended traffic is allowed through the trunk. It also emphasizes the importance of configuration in a switched network environment, where not every VLAN must necessarily be allowed on every trunk, thus providing control over VLAN traffic management.