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Instructor & Todd Lammle

Instructor & Todd Lammle

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Instructor & Todd Lammle

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  1. Instructor & Todd Lammle Sybex CCNA 640-802 Chapter 8: Layer-2 Switching

  2. Chapter 8 Objectives The CCNA Topics Covered in this chapter include: • What is layer-2 switching • Switching services • Bridges vs. LAN switching • Three switch functions • MAC table • Switching loops Spanning-Tree Protocol (STP) 2

  3. Layer 2 Switching • Purposes for using switching • Breaks up collision domains • Cost-effective, resilient internetwork • Purpose for Spanning-Tree Protocol (STP) • Stops loops in layer 2 switched networks

  4. Before Layer 2 Switching

  5. Switched LANs

  6. Typical Switched Designs

  7. One link to the server!

  8. Switching Services Layer 2 switching provides: • Hardware-based bridging (ASIC) • Wire speed • Low latency • Low cost

  9. Limitations of Layer 2 Switching • Must break up the collision domains correctly. • Make sure that users spend 80 percent of their time on the local segment. • Switches do not break up broadcast domains by default.

  10. Bridging vs. LAN switching

  11. Three Switch Functions at Layer-2

  12. Empty MAC table

  13. How Switches Learn Hosts’ Locations

  14. Switching Loops

  15. Switching Loop Problems

  16. Spanning-Tree Protocol (STP)Solves Switching loops at layer 2 • STP • Root Bridge • BPDU • Bridge ID • Nonroot Bridge • Root port • Designated port • Port cost • Nondesignated port • Forwarding port • Block port

  17. Spanning-Tree Operations • Selecting the root bridge • Selecting the designated port

  18. Switching Loops

  19. Spanning-Tree Port States • Blocking • Listening • Forwarding • Disabled

  20. Spanning-Tree Example