Differentiating the roles of Layer 2 switches and Layer 3 routers.
Switches and routers are both essential networking devices that forward data, but they operate at different layers of the OSI model and perform distinct functions. A switch is primarily a Layer 2 (Data Link Layer) device. Its main purpose is to connect devices within the same local area network (LAN). A switch makes forwarding decisions based on physical MAC addresses. It maintains a MAC address table, which maps the MAC addresses of connected devices to the switch's physical ports. When a frame arrives, the switch looks at the destination MAC address, checks its table, and forwards the frame only out of the port connected to the destination device. This creates micro-segments, reducing collisions and improving LAN performance compared to older hubs which simply broadcast all traffic to all ports. A router is a Layer 3 (Network Layer) device. Its primary role is to connect different networks together and forward packets between them—this is the essence of internetworking. Routers make forwarding decisions based on logical IP addresses. They maintain a routing table, which contains information about which network prefixes are reachable via which interface or next-hop router. When a packet arrives, the router examines the destination IP address, performs a lookup in its routing table, and forwards the packet on the best path toward its final destination. Routers create broadcast domains, meaning they do not forward broadcast traffic from one network to another, which is crucial for managing traffic on a large scale.