What is VLAN and how does it work?

 Theme: Networking Protocols  Role: Network Engineer  Function: Technology

  Interview Question for Network Engineer:  See sample answers, motivations & red flags for this common interview question. About Network Engineer: Designs and maintains computer networks. This role falls within the Technology function of a firm. See other interview questions & further information for this role here

 Sample Answer 


  Example response for question delving into Networking Protocols with the key points that need to be covered in an effective response. Customize this to your own experience with concrete examples and evidence

  •  Definition of VLAN: A VLAN (Virtual Local Area Network) is a logical grouping of devices within a network that are grouped together based on specific criteria, such as department, function, or security requirements
  •  Purpose of VLAN: VLANs are used to segment a network into smaller, isolated broadcast domains, improving network performance, security, and manageability
  •  How VLAN Works: VLANs work by assigning devices to specific VLANs based on their port, MAC address, or protocol. Switches use VLAN tagging to identify and separate traffic between VLANs
  •  VLAN Tagging: VLAN tagging is a method used to identify VLAN membership of network frames. It adds a VLAN tag to the Ethernet frame, indicating the VLAN ID to which the frame belongs
  •  VLAN Trunking: VLAN trunking is used to carry multiple VLANs over a single physical link between switches. It allows for the transmission of traffic from multiple VLANs across the network
  •  Benefits of VLANs: 1. Improved network performance by reducing broadcast traffic and optimizing bandwidth usage. 2. Enhanced network security by isolating sensitive data and controlling access between VLANs. 3. Simplified network management by allowing for easier configuration and troubleshooting of specific VLANs. 4. Flexibility in network design and scalability by easily adding or reassigning devices to different VLANs
  •  Types of VLANs: 1. Port-based VLANs: Devices are assigned to VLANs based on the physical switch port they are connected to. 2. MAC-based VLANs: Devices are assigned to VLANs based on their MAC addresses. 3. Protocol-based VLANs: Devices are assigned to VLANs based on the protocols they use, such as IP or IPX
  •  VLAN Best Practices: 1. Proper planning and documentation of VLAN assignments and configurations. 2. Regular monitoring and maintenance of VLANs to ensure proper functioning. 3. Implementing VLAN access control lists (VACLs) to control traffic between VLANs. 4. Using VLAN pruning to limit unnecessary broadcast traffic. 5. Implementing VLAN tagging and trunking protocols, such as IEEE 802.1Q or ISL, for inter-switch communication

 Underlying Motivations 


  What the Interviewer is trying to find out about you and your experiences through this question

  •  Technical knowledge: Assessing the candidate's understanding of VLAN and its functioning
  •  Problem-solving skills: Evaluating the candidate's ability to troubleshoot and configure VLANs
  •  Experience: Determining if the candidate has practical experience in implementing VLANs in a network environment
  •  Communication skills: Assessing the candidate's ability to explain complex technical concepts in a clear and concise manner

 Potential Minefields 


  How to avoid some common minefields when answering this question in order to not raise any red flags

  •  Lack of understanding: Providing a vague or incorrect definition of VLAN or not being able to explain its purpose and functionality
  •  Inability to explain VLAN implementation: Not being able to describe how VLANs are configured, managed, and how they operate within a network
  •  Limited knowledge of VLAN types: Not being aware of different types of VLANs such as port-based, tag-based, or protocol-based VLANs
  •  Failure to address VLAN benefits: Neglecting to mention the advantages of VLANs, such as improved network security, increased flexibility, and better network performance
  •  Lack of troubleshooting skills: Being unable to discuss common VLAN issues or troubleshoot VLAN-related problems
  •  Poor understanding of VLAN scalability: Not being able to explain how VLANs can be scaled or expanded to accommodate growing network requirements
  •  Inability to relate VLAN to other networking concepts: Failing to connect VLANs with other networking concepts like subnetting, routing, or switch configuration

 Related

  Other questions asked for the Network Engineer in Technology function. View details for the Network Engineer here