1. © Wiley Inc. 2006. All Rights Reserved. CCNA: Cisco Certified Network Associate Study Guide CHAPTER 7: Layer 2 Switching

2. © Wiley Inc. 2006. All Rights Reserved. The CCNA exam topics covered in this chapter include the following: Technology Describe the Spanning Tree process

3. © Wiley Inc. 2006. All Rights Reserved. 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. © Wiley Inc. 2006. All Rights Reserved. Before Layer 2 Switching

5. © Wiley Inc. 2006. All Rights Reserved. Switched LANs

6. © Wiley Inc. 2006. All Rights Reserved. Typical Switched Designs

7. © Wiley Inc. 2006. All Rights Reserved. One link to the server!

8. © Wiley Inc. 2006. All Rights Reserved. Switching Services Layer 2 switching provides: –Hardware-based bridging (ASIC) –Wire speed –Low latency –Low cost

9. © Wiley Inc. 2006. All Rights Reserved. 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. © Wiley Inc. 2006. All Rights Reserved. Bridging vs. LAN switching

11. © Wiley Inc. 2006. All Rights Reserved. Three Switch Functions at Layer-2

12. © Wiley Inc. 2006. All Rights Reserved. Empty MAC table

13. © Wiley Inc. 2006. All Rights Reserved. How Switches Learn Hosts’ Locations

14. © Wiley Inc. 2006. All Rights Reserved. Switching Loops

15. © Wiley Inc. 2006. All Rights Reserved. Switching Loop Problems

16. © Wiley Inc. 2006. All Rights Reserved. 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. © Wiley Inc. 2006. All Rights Reserved. Spanning-Tree Operations Selecting the root bridge Selecting the designated port

18. © Wiley Inc. 2006. All Rights Reserved. Switching Loops

19. © Wiley Inc. 2006. All Rights Reserved. Spanning-Tree Port States Blocking Listening Forwarding Disabled

20. © Wiley Inc. 2006. All Rights Reserved. Spanning-Tree Example

21. © Wiley Inc. 2006. All Rights Reserved. LAN Switch Types Cut-through (FastForward) FragmentFree (modified cut-through) Store-and-forward