If a switch just forwarded every frame it received out all ports, your network would be so congested that it would probably come to a complete halt.Ī Layer 2 Ethernet switch uses Layer 2 MAC addresses to make forwarding decisions.
Now that you know all about Ethernet MAC addresses, it is time to talk about how a switch uses these addresses to forward (or discard) frames to other devices on a network. Layer 3 switches are beyond the scope of this book.
This section focuses on Layer 2 switches. Although traditionally most LAN switches have operated at Layer 2 of the OSI model, an increasing number of Layer 3 switches are now being implemented. Compared to legacy Ethernet hubs, Ethernet switches improve efficiency and overall network performance.