The device bridge is used at ____ layer of OSI reference model.

The OSI model classifies each networking device by the layer at which it reads and acts on information. The Physical layer (Layer 1) only regenerates or repeats raw bits, with no awareness of addresses (repeaters, hubs). The Data Link layer (Layer 2) adds hardware (MAC) addressing, so a device here can read a frame's destination address and decide whether to forward or block it (bridges, switches). The Network layer (Layer 3) adds logical (IP) addressing and path selection across different networks (routers). The Transport layer (Layer 4) manages end-to-end delivery between processes (TCP/UDP). The Application layer (Layer 7) defines protocols used directly by user-facing software.

A bridge joins two or more LAN segments into one logical network. It examines the destination MAC address in every incoming Ethernet frame, learns which addresses sit on which segment, and forwards or filters the frame accordingly — it never looks at an IP address or makes a routing decision. Reading and acting on MAC addresses to forward frames is precisely the Data Link layer's function, so a bridge is a Layer 2 device.

• Physical layer (Layer 1): repeaters and hubs here only regenerate electrical/optical signals with no address awareness at all; a bridge sits one layer above, adding address-based forwarding.

• Network layer (Layer 3): routers here use IP addresses to choose a path between different networks; a bridge has no IP-routing logic and stays within one broadcast domain's segments.

• Transport layer (Layer 4): governs end-to-end, process-to-process delivery (TCP/UDP segments) between hosts, unrelated to forwarding frames within a LAN.

• Application layer (Layer 7): defines protocols consumed directly by end-user software (e.g., a browser or mail client), with no role in hardware frame forwarding.

So the bridge's frame-forwarding-by-MAC-address behaviour places it at the Data Link layer (Layer 2) of the OSI model.