Which statement best differentiates a switch from a router?

Which statement best differentiates a switch from a router?

• A. Switches operate mainly at Layer 2 to forward frames within a local network; routers work at Layer 3 to route packets between networks.
• B. Switches route packets between networks; routers forward frames within a local network.
• C. Switches operate at Layer 3; routers operate at Layer 2.
• D. Switches keep track of MAC addresses; routers do not.

Answer: (A)

The key idea here is understanding what each device uses to move data and where it does most of its work. A switch operates mainly at Layer 2 of the OSI model, which means it forwards frames inside a single local network by using MAC addresses. It learns which devices are reachable on which ports and builds a MAC address table, so a frame is sent only to the port that leads to its destination. This keeps communication inside the LAN and helps separate collision domains (and VLANs can further segment broadcast domains). A router, on the other hand, works at Layer 3 and forwards packets between different networks by using IP addresses and routing tables. It decides the next hop to reach a destination network and can connect disparate networks, such as a local network to the internet or another remote network. So the statement that distinguishes them—switches handling Layer 2 forwarding of frames within a local network and routers handling Layer 3 routing of packets between networks—is the best description. Modern devices can blur these lines a bit (for example, Layer 3 switches can perform routing), but the traditional and most common distinction remains that switches operate at Layer 2 for local switching, while routers operate at Layer 3 for inter-network routing.

The key idea here is understanding what each device uses to move data and where it does most of its work. A switch operates mainly at Layer 2 of the OSI model, which means it forwards frames inside a single local network by using MAC addresses. It learns which devices are reachable on which ports and builds a MAC address table, so a frame is sent only to the port that leads to its destination. This keeps communication inside the LAN and helps separate collision domains (and VLANs can further segment broadcast domains).

A router, on the other hand, works at Layer 3 and forwards packets between different networks by using IP addresses and routing tables. It decides the next hop to reach a destination network and can connect disparate networks, such as a local network to the internet or another remote network.

So the statement that distinguishes them—switches handling Layer 2 forwarding of frames within a local network and routers handling Layer 3 routing of packets between networks—is the best description. Modern devices can blur these lines a bit (for example, Layer 3 switches can perform routing), but the traditional and most common distinction remains that switches operate at Layer 2 for local switching, while routers operate at Layer 3 for inter-network routing.