Which device operates at both Layer 2 and Layer 3 of the OSI model?

A device that operates at both Layer 2 (Data Link Layer) and Layer 3 (Network Layer) of the OSI model is typically a multi-layer switch or a switch with Layer 3 capabilities. Layer 2 devices are primarily responsible for switching frames within the same local area network (LAN) using MAC addresses, while Layer 3 devices can route packets between different networks using IP addresses.

A switch, particularly a Layer 3 or multi-layer switch, can perform both functions. It operates at Layer 2 to manage traffic within a local network by forwarding data packets based on MAC addresses. Simultaneously, it can perform Layer 3 routing functions by using IP addresses to forward packets to other networks, allowing it to support inter-VLAN routing and provide features like DHCP and ACLs (Access Control Lists).

In contrast, a router operates solely at Layer 3, focusing on routing packets between different networks. A hub functions only at Layer 1 (Physical Layer), transmitting data to all connected devices indiscriminately without any intelligent forwarding. A bridge operates at Layer 2, similar to a switch, but is not capable of Layer 3 routing functionalities.

Thus, the choice of a switch is correct as it embodies the characteristics of both