In a switched network environment, Virtual LANs (VLANs) are deployed to segment broadcast domains. Which of the following statements regarding VLANs and trunking are correct? (Select all that apply.)
Correct Answer: A,B,D,E
Detailed Explanation: Virtual LANs (VLANs) are a key component in modern network design that enable the logical segmentation of a physical network into multiple isolated broadcast domains. By doing so, VLANs allow network administrators to group users and resources logically, independent of their physical location, which leads to improved security, better traffic management, and enhanced overall network performance (Option A). For example, a company might create separate VLANs for different departments such as Finance, HR, and IT to segregate sensitive data and limit broadcast traffic to relevant segments. The use of VLANs necessitates a method for carrying traffic from multiple VLANs across the same physical medium. This is where trunk links come into play. Trunk links are configured on switch ports and are designed to transport traffic for multiple VLANs simultaneously by using a tagging protocol, most commonly IEEE 802.1Q (Option B). In this protocol, frames transmitted over a trunk are tagged with a VLAN identifier so that the receiving switch knows to which VLAN each frame belongs. This tagging mechanism is critical for maintaining VLAN integrity across switches in a network. A common misconception is that a trunk port can carry traffic for only one VLAN; however, the very purpose of trunking is to allow a single link to handle multiple VLANs concurrently. Option C is therefore incorrect because a trunk port’s role is to aggregate traffic from several VLANs—not to limit it to a single VLAN. In contrast, access ports are typically assigned to a single VLAN and do not perform tagging. VLAN tagging (Option D) is essential in environments where traffic from multiple VLANs shares the same physical medium. When a frame traverses a trunk link, the 802.1Q tag is inserted into the frame, indicating its VLAN membership. At the receiving end, the tag is examined, and the frame is forwarded to the appropriate VLAN. This mechanism ensures that data remains correctly segregated even as it passes through shared infrastructure. Finally, VLANs help reduce unnecessary broadcast traffic and network congestion (Option E) by confining broadcast domains to a smaller, logical segment of the network. Without VLANs, a broadcast sent on one segment of a large network could inundate all devices on that segment. By limiting the scope of broadcast traffic to individual VLANs, network performance and security are enhanced. Broadcast storms are contained, and network resources are used more efficiently. Together, these aspects of VLANs and trunking form a robust framework for modern network segmentation, facilitating improved security, performance, and manageability in a scalable manner.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.