Part 3. Layer 2 concepts

In part 3, we will build upon your foundational understanding of how switches provide connectivity within a LAN. You have already grasped the basics of MAC address learning and aging, frame forwarding and flooding, and other key operations of switches. Now, let’s delve deeper into several advanced features that optimize and secure LANs. We’ll start in chapter 12 by exploring virtual LANs (VLANs), which allow us to divide a single physical switch into multiple virtual switches, dividing the LAN into multiple separate segments and enhancing its security and efficiency.

In chapter 13, we will continue on the topic of VLANs, covering two auxiliary protocols that streamline the configuration and management of VLANs on Cisco switches: Dynamic Trunking Protocol (DTP) and VLAN Trunking Protocol (VTP). We will then shift our attention to Spanning Tree Protocol (STP) in chapter 14 and Rapid Spanning Tree Protocol (RSTP) in chapter 15. These protocols are vital for preventing broadcast storms—broadcast frames that infinitely loop around the switches in the LAN, clogging up the LAN and preventing hosts in the LAN from communicating.