1. This document introduces the feature overview and configuration methods of Ethernet switches. 2. Ethernet switches are used to connect multiple Local Area Network (LAN) segments together to form an extended LAN. 3. Stations connected to different LANs can be configured to communicate with each other as if they were on the same LAN. 4. They can also divide one physical LAN into multipleVirtual LANs (VLANs). 5. Stations connected to each other on the same extended LAN can be grouped in separateVLANs, so that a station in oneVLAN can communicate at Layer 2 with other stations in the sameVLAN, but must go through higher layer routing protocols to communicate with stations in otherVLANs. 6. Ethernet switches appear transparent to higher layer protocols, transferring frames between the data link layers of the networks to which they are attached. 7. A Layer 2 switch accesses each physical link according to the rules for that particular network. 8. Access may not always be instant if a link's bandwidth is oversubscribed, so the switch must be capable of storing and forwarding frames. 9. Storing and forwarding enables the switch to examine both theVLAN tag fields and Ethernet MAC address fields in order to forward the frames to their appropriate destination. 10. In this way, the switch can act as an intelligent filtering device, redirecting or blocking the movement of frames between networks. 11. Because switch ports can sometimes receive broadcasts, multicasts, and group multicast frames from networks and VLANs, the Ethernet switch must forward these frames to all other ports connected to the switch.
