What is the difference between a router and a Layer 3 switch?

What is the difference between a router and a Layer 3 switch?

• A. A router connects multiple networks and runs routing protocols; a Layer 3 switch forwards between VLANs within a LAN and can perform routing at high speed.
• B. A router forwards between VLANs within a LAN, while a Layer 3 switch routes between different networks.
• C. A router operates at layer 1; a Layer 3 switch operates at layer 4.
• D. A router cannot interconnect VLANs; a Layer 3 switch does not perform routing.

Answer: (A)

Routing across networks versus routing inside a local LAN is what this question is comparing. A router connects multiple networks and runs routing protocols to learn paths to remote networks, including routes toward other organizations or the internet. It’s the device you’d use to link a LAN to the WAN or to another network with different IP networks, and it supports dynamic protocols like OSPF, BGP, or EIGRP to make decisions about where to send traffic. A Layer 3 switch, on the other hand, sits inside the LAN and handles routing between VLANs within that same local network. It uses inter-VLAN routing—often via switched virtual interfaces (SVIs)—to forward traffic between different VLANs quickly using hardware-based routing. While it can run routing protocols too, the emphasis is on fast routing of intra-LAN traffic between segments, rather than connecting to distant networks. The other statements don’t fit because they either swap the roles (router routing between VLANs vs Layer 3 switch routing between networks), misstate the OSI layer (routing happens at Layer 3, not Layer 1 or 4), or claim something that isn’t true about these devices’ capabilities.

Routing across networks versus routing inside a local LAN is what this question is comparing. A router connects multiple networks and runs routing protocols to learn paths to remote networks, including routes toward other organizations or the internet. It’s the device you’d use to link a LAN to the WAN or to another network with different IP networks, and it supports dynamic protocols like OSPF, BGP, or EIGRP to make decisions about where to send traffic.

A Layer 3 switch, on the other hand, sits inside the LAN and handles routing between VLANs within that same local network. It uses inter-VLAN routing—often via switched virtual interfaces (SVIs)—to forward traffic between different VLANs quickly using hardware-based routing. While it can run routing protocols too, the emphasis is on fast routing of intra-LAN traffic between segments, rather than connecting to distant networks.

The other statements don’t fit because they either swap the roles (router routing between VLANs vs Layer 3 switch routing between networks), misstate the OSI layer (routing happens at Layer 3, not Layer 1 or 4), or claim something that isn’t true about these devices’ capabilities.