Layer2SwitchingFunktion

Layer 2 switching refers to the process of forwarding frames based on MAC addresses within a local area network. It operates at the OSI model’s Data Link layer and is the primary method used by network switches to connect devices on the same network segment.

Layer 2 switches learn which devices can be reached through which physical ports by inspecting the source MAC address of each frame they receive. This information is stored in a MAC address table. When a frame arrives, the switch consults the table to determine the correct egress port. If the destination MAC is unknown, the switch floods the frame to all ports in the same VLAN, until the destination responds and an entry is learned. Entries age out over time to reflect changes in the network.

VLANs are commonly used with Layer 2 switches to segment broadcast domains. Ports can be configured as access ports, carrying untagged traffic for a single VLAN, or trunk ports, carrying traffic for multiple VLANs with 802.1Q tags. To prevent switching loops in networks with redundant paths, switches implement Spanning Tree Protocol variants such as STP, RSTP, or MSTP, which converge on a loop-free topology.

Performance and security considerations play a key role in design. Layer 2 switching enables high-speed, full-duplex connections and efficient intra-network communication, but it confines traffic to a single broadcast domain unless VLANs or layer 3 boundaries are used. Security features such as port security, MAC filtering, DHCP snooping, and 802.1X help mitigate risks associated with unauthorized devices or malicious traffic.

In practice, Layer 2 switching forms the access layer of most enterprise networks, while Layer 3 routing handles inter-network communication. Switches provide foundational connectivity, scalability, and ease of management for local-area networks.