1. CCNA 1 v3.0 Module 8 Ethernet Switching

2. Copyright © 2005 University of Bolton Issues with Ethernet On busier shared ethernet networks, collisions become a problem, restricting available bandwidth Bridges and Switches introduced to help Also worry about Broadcast frames Broadcasts can occupy all stations on a network

3. Copyright © 2005 University of Bolton Role of Bridges More nodes on a segment constrains bandwidth Bridges break up large segments into smaller ones Introducing a switch means that there will be more collision domains, each of which will be smaller

4. Copyright © 2005 University of Bolton Bridge Operation From:To: Port A Port B 000001CCCCCC 000001BBBBBB 000001DDDDDD 000001AAAAAA 000001BBBBBB AddressPort 000001AAAAAA A 000001BBBBBB A 000001CCCCCC B 000001DDDDDDB 000001BBBBBB000001AAAAAA000001CCCCCC000001AAAAAA 000001CCCCCC 000001DDDDDD 000001AAAAAA000001DDDDDD000001CCCCCC

5. Copyright © 2005 University of Bolton Bridges

6. Copyright © 2005 University of Bolton Switch Operation Layer 2 switches rely on MAC addresses to direct packets in the same way a bridge does Essentially a switch is a multi-port bridge Each switch port is effectively a separate collision domain Switches use Content Addressable Memory (CAM)

7. Copyright © 2005 University of Bolton Ethernet Switching Station connected directly to a switch forms a two- node microsegment Can operate full duplex, double capacity with no collision domain CAM means no time taken to search MAC tables Dedicated hardware speeds up switching process

8. Copyright © 2005 University of Bolton Network Latency Media delays - finite speed of travel along media Circuit delays - time taken by electronic components to process signals Software delays - time taken to make decisions when switching traffic Content delays - takes time to read destination address in frame

9. Copyright © 2005 University of Bolton Switch Modes Switch operation a trade off between reliability and speed Cut-through switching forwards as soon as destination MAC address read (no error checking) Store and forward mode waits for entire frame before forwarding Fragment free reads first 64 bytes - all of header and some of data

10. Copyright © 2005 University of Bolton Switch Modes If cut-through mode used, switch ports must be same bit-rate Known as symmetric switching If different port speeds are required (asymmetric switching) store and forward must be used

11. Copyright © 2005 University of Bolton Switched networks Typically cross-connect switches Allows for reliability Single switch can fail without blocking network Potentially causes loops

12. Copyright © 2005 University of Bolton STP States

13. Copyright © 2005 University of Bolton Types of Networks

14. Copyright © 2005 University of Bolton Collisions in Collision Domain

15. Copyright © 2005 University of Bolton Layer 1 Devices Extend Collision Domains

16. Copyright © 2005 University of Bolton Broadcasts in a Bridged Environment

17. Copyright © 2005 University of Bolton Broadcast Domain Segmentation

18. Copyright © 2005 University of Bolton Data Flow Through a Network

19. Copyright © 2005 University of Bolton What is a Network Segment?