What are two reasons a VLAN would be used on a Layer 2 switch? (Choose two.)
- to allow a router to broadcast traffic between two networks
- to allow traffic to be sent between two networks
- to filter network traffic based on protocol port numbers
- to create separate broadcast domains on a switch
- to allow multiple networks to be created at Layer 2
Reasons to Use VLANs on a Layer 2 Switch
Virtual Local Area Networks (VLANs) are a powerful tool for network administrators, offering several benefits when implemented on Layer 2 switches. Here are two key reasons why VLANs are used:
1. Creating Separate Broadcast Domains
One of the primary functions of VLANs is to create separate broadcast domains within a switch. In a network, a broadcast domain is a group of devices that receive broadcast frames originating from any device within the group. By default, all devices connected to a switch are in a single broadcast domain. This means that broadcast traffic (such as ARP requests) from any device will be sent to all other devices on the network.
VLANs allow you to segment a switch into multiple logical networks. Each VLAN acts as its own broadcast domain, so broadcasts sent by a device in one VLAN will not be received by devices in another VLAN. This segmentation reduces unnecessary broadcast traffic and enhances network performance and security. For example, if you have VLAN 10 and VLAN 20, a broadcast sent by a device in VLAN 10 will stay within VLAN 10 and will not affect devices in VLAN 20.
2. Allowing Multiple Networks at Layer 2
VLANs enable the creation of multiple logical networks on the same physical switch infrastructure. This means you can have different VLANs for different departments or functions within an organization (e.g., VLAN for HR, VLAN for IT, VLAN for guests) all running over the same physical hardware.
This logical separation offers several benefits:
- Better Network Management: VLANs make it easier to manage and troubleshoot network issues. Each VLAN can be administered independently, allowing for tailored network policies and access control.
- Enhanced Security: By isolating different types of traffic into separate VLANs, you can apply specific security policies to each VLAN. For example, sensitive data from the finance department can be isolated from general user traffic, reducing the risk of data breaches.
- Improved Performance: VLANs reduce broadcast traffic within each segment, leading to better network performance and efficiency.
Analyzing All Options
When considering why VLANs are used, it’s important to understand each potential reason and its validity:
To allow a router to broadcast traffic between two networks
Analysis: VLANs do not inherently allow a router to broadcast traffic between two networks. Routers can route traffic between different VLANs, but the act of broadcasting is a Layer 2 function and is confined to VLANs. This option is incorrect because it conflates the roles of Layer 2 VLANs and Layer 3 routing.
To allow traffic to be sent between two networks
Analysis: While VLANs can segregate networks, they do not by themselves enable traffic to be sent between networks. Traffic between VLANs requires a Layer 3 device (router or Layer 3 switch) to perform inter-VLAN routing. This option is incorrect because VLANs alone do not facilitate inter-network traffic.
To filter network traffic based on protocol port numbers
Analysis: Filtering network traffic based on protocol port numbers is typically a function of a firewall or a Layer 3 device using access control lists (ACLs). VLANs segment traffic at Layer 2 based on membership, not protocol port numbers. This option is incorrect because VLANs do not perform protocol-based filtering.
To create separate broadcast domains on a switch
Analysis: This is a primary function of VLANs. By creating separate VLANs, a switch can separate broadcast domains, ensuring that broadcasts in one VLAN are not propagated to other VLANs. This helps reduce unnecessary broadcast traffic and enhances network performance and security. This option is correct.
To allow multiple networks to be created at Layer 2
Analysis: VLANs allow a single physical switch to support multiple logical networks, each functioning as an independent network segment at Layer 2. This logical segmentation enables better organization and management of the network. This option is correct.
Conclusion
Implementing VLANs on a Layer 2 switch is a practical way to enhance network performance, security, and manageability. By creating separate broadcast domains and allowing multiple networks to coexist on the same physical infrastructure, VLANs provide a flexible and efficient solution for modern network environments.
The correct reasons for using VLANs on a Layer 2 switch are:
- To create separate broadcast domains on a switch
- To allow multiple networks to be created at Layer 2