Part III: Implementing VLANs and STP

Part II of this book introduces the basics of Ethernet LANs, both in concept and in how to implement the features. However, the two primary features discussed in Part III of this book—Virtual LANs (VLANs) and Spanning Tree Protocol (STP)—impact almost everything you have learned about Ethernet so far. VLANs allow a network engineer to create separate Ethernet LANs through simple configuration choices. The ability to separate some switch ports into one VLAN and other switch ports into another VLAN gives network designers a powerful tool for creating networks. Once created, VLANs also have a huge impact on how a switch works, which then impacts how you verify and troubleshoot the operation of a campus LAN.

STP—and the related and similar Rapid STP (RSTP)—acts to prevent frames from looping around a LAN. Without STP or RSTP, in LANs with redundant links, broadcasts and some other frames would be forwarded around and around the LAN, eventually clogging the LAN so much as to make it unusable.

The current CCNA 200-301 exam blueprint includes exam topics for the configuration and verification of VLANs and related topics. However, the CCNA exam topics only mention RSTP concepts rather than configuration/verification. To that end, Part III opens with Chapter 8, which goes to the configuration/verification depth with VLAN topics, followed by Chapter 9, which introduces the concepts of STP and RSTP.

Part III closes with Chapter 10, which includes some RSTP configuration, along with Layer 2 EtherChannel configuration.

Other Resources

As one additional suggestion for those who intend to move on to CCNP Enterprise, consider skimming or reading Appendix P, “LAN Troubleshooting,” found on the online companion website. This appendix, a copy of a chapter from the previous edition of the book, takes a troubleshooting approach to many of the topics found in Parts II and III of this book. Although Cisco completely removed the word troubleshoot from the CCNA exam blueprint in its current CCNA 200-301 version, the topics still remain relevant and can be a help for reviewing and refining what you learned in Parts II and III of this book.

Chapter 8: Implementing Ethernet Virtual LANs

Chapter 9: Spanning Tree Protocol Concepts

Chapter 10: RSTP and EtherChannel Configuration

Part III Review

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