Which device links two homogeneous packet-broadcast Local Area Networks (for example, two Ethernet segments) by forwarding frames based on MAC addresses?

Introduction / Context:
Interconnecting LAN segments can be done at different OSI layers. When the networks are homogeneous (same Layer-2 technology) and you want to forward frames based on MAC addresses while preserving a single Layer-3 subnet, the classic device is a bridge. Modern switches are multiport bridges, performing the same fundamental function with hardware acceleration.

Given Data / Assumptions:

• Two LANs share the same L2 protocol (e.g., Ethernet).
• Forwarding should occur using MAC learning and filtering.
• No Layer-3 routing or protocol translation is required.

Concept / Approach:
A bridge learns source MAC addresses per port and forwards unknown-unicast, multicast, or broadcast frames accordingly while filtering frames that do not need to cross segments. This reduces collisions (in older shared media) and contains unnecessary traffic. Repeaters/hubs operate at Layer-1, simply regenerating bits, and do not learn MACs. Routers operate at Layer-3 and separate IP subnets. Gateways typically imply protocol translation or higher-layer mediation.

Step-by-Step Solution:

Verification / Alternative check:
Spanning Tree Protocol (STP) is a Layer-2 control protocol used by bridges/switches to prevent loops—further evidence that bridges are the appropriate L2 interconnect for homogeneous networks.

Why Other Options Are Wrong:

• Repeater/Hub: no MAC learning; simply regenerate and repeat signals.
• Router: forwards based on IP/subnet; separates broadcast domains.
• Gateway: often implies heterogeneous protocol translation beyond simple L2 forwarding.

Common Pitfalls:
Using “gateway” generically to describe any interconnect; forgetting that modern switches are functionally bridges with many ports.

Final Answer:
Bridge