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CCNA 1 Chapter 6, part 2 Ethernet Switching

CCNA 1 Chapter 6, part 2 Ethernet Switching. By Your Name. Objectives. Ethernet switching Collision domains and broadcast domains. Layer 2 Bridging.

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CCNA 1 Chapter 6, part 2 Ethernet Switching

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  1. CCNA 1 Chapter 6, part 2Ethernet Switching By Your Name

  2. Objectives • Ethernet switching • Collision domains and broadcast domains

  3. Layer 2 Bridging • Based on the Ethernet frame design, the need arose for a device that could hold a learned list of MAC addresses and direct frames to a specific port, based on the MAC address of the destination node. • Describe the process.

  4. Bridge Types Source route bridges are used primarily with Token Ring network segments. A bridge connects network segments and makes intelligent decisions about whether to pass signals on to the next segment.

  5. Bridge Operations

  6. Switches

  7. Switch Benefits

  8. Switching Table

  9. Latency • Latency is the delay between the time a frame first starts to leave the source device and the time the first part of the frame reaches its destination.

  10. Switch Modes • Cut-through switching — A switch can start to transfer the frame as soon as the destination MAC address is received. • Store-and-forward switching —The switch can receive the entire frame before sending it out the destination port. This gives the switch software an opportunity to verify the frame check sum (FCS).

  11. SpanningTree Protocol • Loops can occur when extra switches and bridges are added to provide redundant paths for reliability and fault tolerance. • A switch sends special messages called bridge protocol data units (BPDUs) out all its ports to let other switches know of its existence. • The switches use a spanning-tree algorithm (STA) to resolve and shut down the redundant paths • The protocol used to resolve and eliminate loops is known as the SpanningTree Protocol (STP).

  12. Collision Domains and Broadcast Domains

  13. Shared Media Environments • It is important to be able to identify a shared media environment, because collisions only occur in a shared environment. • Some networks are directly connected and all hosts share Layer 1: • Shared media • Extended shared media • Point-to-point network

  14. Collisions and Collision Domains • Shared media environment • Collisions and collision domains • Signals in a collision • Repeaters, hubs, and collision domains • The four-repeater rule • Segmenting collision domains

  15. Types of Networks

  16. Data Collisions When two bits are propagated at the same time on the same network, a collision will occur.

  17. Collisions and Collision Domains • Collisions are not inherently bad. • They are a normal function of Legacy Ethernet. • Data on the network during a collision is lost and usually must be retransmitted. • Increased collisions indicate congestion. • All devices on a network that would cause a collision if they transmitted simultaneously are in a collision domain. • Networks with only Layer 1 components are a single collision domain.

  18. Shared media Extended by a hub Extended by a repeater Extended by a huband repeater Shared Media, Repeaters, Hubs, and Collision Domains Each is a single collision domain!

  19. A B The Four-Repeater Rule Legacy Ethernet network: No more than 4 repeaters or repeating hubs can be between any 2 computers on the network. • From A to B is 4 repeaters.

  20. A B Four-Repeater Rule Example • The 5-story building shown violates the four-repeater rule because host A and B are 5 repeaters apart. • Hubs would cause the same result. • Even if all servers were on the third floor, and A and B would never communicate directly; they are too far to hear each other transmit and can cause data collisions. • What are implications for taller buildings?

  21. A Hub B Four-Repeater Rule Example Layer 1 Solution • The hub added, which could be on any floor, allows us to comply with the four-repeater rule. • No 2 hosts are more than 3 repeaters apart. • What are implications for taller buildings? It really wouldn’t matter if each floor connects to the hub. • How many collision domains do we have? Still only one and getting bigger with each floor.

  22. Too Much Traffic / Too Many Hosts in a Collision Domain…

  23. Ethernet LAN Segmentation

  24. Segmenting with Bridges

  25. Segmenting with Switches

  26. Segmenting with Routers

  27. Microsegmentation Hubs

  28. Layer 2 Broadcasts • Layer 2 devices must flood all broadcast and multicast traffic. • The accumulation of broadcast and multicast traffic from each device in the network is referred to as broadcast radiation.

  29. Broadcast Domains The only devices that can segment collision domains are bridges, switches (both Layer 2), and routers (Layer 3).

  30. Data Flow

  31. Network Segment • If the segment is used in TCP, it would be defined as a separate piece of the data. • If segment is being used in the context of physical networking media in a routed network, it would be seen as one of the parts or sections of the total network.

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