Layer 3 Device Functions | Explained in Cisco Exam 200-301

Primary Function of a Layer 3 Device


What is the primary function of a Layer 3 device?



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A. B. C. D.


The primary function of a Layer 3 device is to pass traffic between different networks, which is also known as routing.

Layer 3 devices, such as routers, operate at the network layer of the OSI model and make decisions about how to forward packets based on their destination IP address. They maintain a routing table that contains information about the networks that they are directly connected to as well as information about other networks that can be reached through those connections.

When a Layer 3 device receives a packet, it looks at the destination IP address and consults its routing table to determine the best path to forward the packet to reach its destination. It then encapsulates the packet in a new frame with the appropriate source and destination MAC addresses for the next hop and forwards it out the appropriate interface.

In contrast, Layer 2 devices, such as switches, operate at the data link layer and are responsible for forwarding frames within the same broadcast domain based on their MAC addresses.

Therefore, option D, to pass traffic between different networks, is the correct answer as it accurately describes the primary function of a Layer 3 device.