Layer 2 switches, also known as Ethernet switches or network switches, operate at the Data Link Layer (Layer 2) of the OSI (Open Systems Interconnection) model. These switches are fundamental components of local area networks (LANs) and are responsible for forwarding Ethernet frames based on Media Access Control (MAC) addresses.

Here are key features and functions of Layer 2 switches:

  1. MAC Address Learning: Layer 2 switches build and maintain a MAC address table (also called a CAM table or forwarding table) by learning the MAC addresses of devices connected to their ports. This table associates MAC addresses with the corresponding switch ports.
  2. Frame Forwarding: Layer 2 switches use the MAC address table to make forwarding decisions. When a frame arrives at a switch, it examines the destination MAC address in the frame header and uses the table to determine which port to forward the frame to. If the MAC address is not in the table, the switch floods the frame to all ports except the one it arrived on.
  3. Broadcast and Collision Domains: Layer 2 switches create separate broadcast domains for each of their ports, reducing network traffic. They also eliminate collisions since each port operates in full-duplex mode, allowing simultaneous data transmission and reception.
  4. VLAN Support: Many Layer 2 switches support Virtual LANs (VLANs), which enable network segmentation. VLANs separate devices into logical groups, enhancing network security and traffic management.
  5. Loop Prevention: Layer 2 switches use the Spanning Tree Protocol (STP) or Rapid Spanning Tree Protocol (RSTP) to prevent loops in Ethernet networks. Loops can lead to broadcast storms and network instability.
  6. Link Aggregation: Layer 2 switches often support link aggregation or port bonding, allowing multiple physical ports to be combined into a single logical link for increased bandwidth and redundancy.
  7. Port Mirroring: Port mirroring, also known as port monitoring, is a feature that allows traffic on one port to be copied to another port for network monitoring and analysis purposes.
  8. Quality of Service (QoS): Some Layer 2 switches offer QoS features to prioritize certain types of traffic based on Ethernet frame attributes such as VLAN tags or DiffServ (Differentiated Services) code points.
  9. Management: Layer 2 switches may provide management interfaces, such as a web-based graphical user interface (GUI) or a command-line interface (CLI), to configure switch settings, view statistics, and monitor network performance.
  10. Security: Switches can implement security features such as MAC address filtering or port security to control which devices are allowed to connect to specific ports.
  11. Energy Efficiency: Many modern Layer 2 switches include energy-saving features like IEEE 802.3az (Energy-Efficient Ethernet) that reduce power consumption during periods of low network activity.

Layer 2 switches are commonly used in Ethernet LANs and provide efficient and high-speed data forwarding within the same network segment. While they are effective for local traffic management, they lack the routing capabilities of Layer 3 switches, which are required for routing traffic between different network segments or subnets. In more complex networks, Layer 2 switches are often combined with Layer 3 routers to provide both local and inter-network connectivity.