Chapter 1: Introducing Layer 2 Switches
Describing data link OSI Layer 2 and how it relates to Layer 2 switches
Describing the purpose of a Layer 2 switch
Differentiating a Layer 2 switch from a hub or a bridge
Describing the basic Layer 2 switch functions
Managing Layer 2 switch port security
Describing how a Layer 2 switch handles unicast, multicast, and broadcast transmissions
Describing MAC address table thrashing and broadcast storms
Read this chapter to find out about Layer 2 switches.
Layer 2 — Data Link Layer Review
Layer 2 in the Open Systems Interconnection (OSI) and TCP/IP network models is the data link layer. The data link layer transmits data on the physical medium. The data link layer uses physical addresses assigned to each physical network device in the local network to route data from one physical device to another. These addresses are called Media Access Control (MAC) addresses in TCP/IP. MAC addresses uniquely identify a specific network device, such as a switch or a router, or a network interface card (NIC), in a host device.
The data link layer has the following features:
♦ Receives each packet from the network layer on the sending host
♦ Wraps up the packet in a data frame along with local routing data (the physical MAC address)
♦ Sends the data frame to the physical layer to code an electrical or optical signal
The physical layer transmits the data frame over a wire or over the air (wireless transmission).
On the receiving host, the data ...