When a switch receives a broadcast frame (that is, a frame destined for MAC address FFFF.FFFF.FFFF), the switch floods the frame out all switch ports other than the port on which the frame was received. Because a layer 2 frame does not have a TTL field, a broadcast frame endlessly circulates through the Layer 2 topology, consuming resources on both switches and attached devices (for example, user PCs).
Figure 11-14 and the following list illustrates how a broadcast storm can form in a Layer 2 topology when STP (Spanning Tree Protocol) is not functioning correctly:
Step 1.
PC1 sends a broadcast frame on to segment A, and the frame enters each switch on port Gig 0/1.
Step 2.
Both switches flood a copy of the broadcast frame out their Gig 0/2 ports (that is, on to segment B), causing PC2 to receive two copies of the broadcast frame.
Step 3.
Both switches receive a copy of the broadcast frame on their Gig 0/2 ports (that is, on to segment B) and flood the frame out their Gig 0/1 ports (that is, on to segment A), causing PC1 to receive two copies of the broadcast frame.
STP prevents Layer 2 loops - which might result in a broadcast storm or corruption of a switch's MAC address table - from occurring in a network.
STP Operation described on page 301 of Learn more about the CompTIA Network+ N10-008 Cert Guide at amazon.com
About The Author
Anthony Sequeira, CCIE No. 15626, is a Cisco Certified Systems Instructor (CCSI) and author regarding all levels and tracks of Cisco Certification. Anthony formally began his career in the information technology industry in 1994 with IBM in Tampa, Florida. He quickly formed his own computer consultancy, Computer Solutions, and then discovered his true passion-teaching and writing about Microsoft and Cisco technologies. Anthony joined Mastering Computers in 1996 and lectured to massive audiences around the world about the latest in computer technologies. Mastering Computers became the revolutionary online training company, KnowledgeNet, and Anthony trained there for many years. Anthony is currently pursuing his second CCIE in the area of Security and is a full-time instructor for the next-generation of KnowledgeNet, StormWind.com. Anthony is also a VMware Certified Professional.
CompTIA Network+ N10-008 Cert Guide contains proven study features that allow you to succeed on the exam the first time. Expert instructor Anthony Sequeira shares preparation hints and test-taking tips, helping you identify areas of weakness and improve both your conceptual knowledge and hands-on skills, essential for successful completion of the performance-based testing items on the exam. This complete, CompTIA-approved study package includes the following:
• A test-preparation routine proven to help you pass the exams
• Clearly defined chapter learning objectives covering all N10-008 exam topics
• Chapter-ending review questions and exam preparation exercises, which help you drill on key concepts you must know thoroughly
• The powerful Pearson Test Prep practice test software, complete with hundreds of well-reviewed, exam-realistic questions, customization options, and detailed performance reports
• 40 performance-based exercises to help you prepare for the hands-on exam questions
• A free copy of the CompTIA Network+ N10-008 Simulator Lite software, complete with meaningful lab exercises that enhance your hands-on skills
• More than 60 minutes of video mentoring
• A final preparation chapter that guides you through tools and resources to help you craft your review and test taking strategies
• An Exam Essentials appendix that quickly recaps all major chapter topics for easy reference, both in print and interactive digital format
• A key terms Glossary in both print and on the companion website, which acts as an interactive flash-card application
• Study plan suggestions and templates to help you organize and optimize your study time
• A 10% exam discount voucher (a $33+ value!)
Well regarded for its level of detail, study plans, assessment features, challenging review questions and exercises, video instruction, and hands-on labs, this approved study guide helps you master the concepts and techniques that ensure your exam success.
Master the topics on the CompTIA Network+ N10-008 exam, including:
• Network topologies and media types
• IP addressing
• Network services
• Data center architectures and cloud concepts
• Routing, Ethernet switching, and wireless networking
• Network availability and disaster recovery
• Network security
• Remote access
• Network troubleshooting
Reader Paulo Cardoso says, "This is a great book. In addition, it comes with great additional resources."
Learn more about the CompTIA Network+ N10-008 Cert Guide at amazon.com
More Networking Topologies Articles:
• Introduction to SONET (Synchronous Optical Networking)
• Cable: Cat5, Cat5e, Cat6, Cat6A ; What's the Difference?
• ISP Multihoming Explained
• What is Fiber Optic Splicing?
• Wireless or Wired Network?
• Network Interface Cards (NIC)
• Data Center Networking
• MPO Connector, MTP Connector, What's the Difference?
• Ethernet Bridges
• Understanding Wireless LAN Networking