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Chabot College

Chabot College. ELEC 99.05 Ethernet Switches. Ethernet Switch Basics. Layer 2 device Uses MAC addressing to control traffic flow Supports multiple simultaneous conversations Reduces needless LAN traffic. Basics: Layer 2 Device. Switch understands layer 2 addresses (MAC addresses):.

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Chabot College

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  1. Chabot College ELEC 99.05 Ethernet Switches

  2. Ethernet Switch Basics • Layer 2 device • Uses MAC addressing to control traffic flow • Supports multiple simultaneous conversations • Reduces needless LAN traffic

  3. Basics: Layer 2 Device • Switch understands layer 2 addresses (MAC addresses): 00-C0-F0-56-BD-98

  4. Basics: MAC Address Use • Switch does not act like hub! • Switch forwards frames based on MACaddress tables.

  5. Basics: MAC Address Use • Switch “learns” MAC addresses of hosts connected to switch ports as it receives frames from those ports:

  6. Basics: Multiple Data Paths • Switch can create several simultaneous data paths or “conversations”:

  7. Switches Reduce Needless LAN Traffic • Each switch port defines a collision domain. • Users on hub Aonly see trafficfrom/to theirworkgroup.

  8. Advanced Features • Switching matrix • Addressing • Multiple data rates • Full duplex • Port trunking • VLANs • Inter-switch communications • Modular Chassis

  9. Switching Matrix (Fabric) • Store & Forward • stores entire incoming frame in memory buffer • performs error detection • drops bad frames • forwards good frames to destination port based on MAC address • takes time - “high latency”

  10. Switching Matrix (Fabric) • Cut-through (cross-point) • reads frame only as far as destination address field • immediately forwards all frames to destination port based on MAC address • no error checking; forwards bad frames(usually not a serious problem) • fast - “low latency” (“wire speed”)

  11. Addressing Capability • 1 MAC address per port • used with “port switching” • microsegmentation

  12. Addressing Capability • 1 MAC address per port • used with “port switching” • microsegmentation • Multiple MAC addresses per port • used with “segment switching”

  13. Multiple Data Transfer Rates • Ports at 10mb/s and 100 mb/s • Requires “flow control” Otherwise, a fast server on a 100 mb portcould overflow the buffer of a 10 mb port.

  14. Full Duplex Ports • Ports can transmit & receive simultaneously. • Useful mainly for servers. • Possible only when there is one host per port (no collisions). • Modern NICs “auto-sense” a full-duplex switch port& turn on FD.

  15. Port Trunking • Ports can “trunked” (linked together) to form a high bandwidth channel between switches:

  16. Tiered Bandwidth • Bandwidth can be placed where it is needed most:

  17. VLANs • Switch ports can be separated into groups called VLANs (virtual LANs)

  18. VLANs • Each VLAN forms a broadcast domain. • Each VLAN is a separate Local Area Network

  19. VLANs • VLAN can be cross-connected by routers.(just like LANs)

  20. Inter-Switch Communication • Vendor-specific frame technologies allow switches to communicate. • Cisco’s version is ISL (Inter Switch Link) • Allows VLANs to span several switches. • Hosts G, I, J, K are all part of VLAN 2:

  21. Modular Chassis • Large switches often use a modular chassis that accepts various: • “switching engines” • interface modules • power supplies • The Cisco Catalyst 5000 and 5505 are examples used on the Chabot campus

  22. Catalyst 5000 Chassis

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