Notes
Slide Show
Outline
1
Interconnecting Cisco Networking Devices
  • Module 5
  • Layer 2 Switching
2
Overview

  • Before Layer 2 Switching
  • Switching Services
  • Spanning Tree Protocol (STP)
  • LAN Switch Types
  • Useful Commands
3
Before Layer 2 Switching

  • “Collapsed Backbone”


  • First Switched LANs


  • Today’s Environment
4
Layer 2 Switching Services

  • Hardware-based Bridging (ASIC)


  • Wire speed


  • Low latency


  • Low cost
5
Limitations of Layer 2 Switching
  • Must design network correctly


  • Make sure users spend 80% of their time on the local segment (80/20 rule)
6
Three Switch Functions at Layer 2

  • Address Learning


  • Forward / Filter Decisions


  • Loop Avoidance
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Spanning Tree Protocol (STP)
  • Attempts to stop network loops from occurring on the layer 2 network
  • Useful Terms
  • STP
  • Root Bridge
  • BPDU
  • BridgeID
  • Nonroot Bridge
  • Root Port
  • Designated Port
  • Port Cost
  • Nondesignated Port
  • Forwarding Port
  • Blocked Port
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Spanning Tree Protocol (STP)
  • Spanning Tree States
  • Blocking (*)
  • Listening
  • Learning
  • Forwarding (*)
  • Disabled
  • Convergence


  • Default is 50 seconds
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LAN Switch Types

  • Cut-through (FastForward)


  • FragmentFree (modified Cut-Through)


  • Store-and-Forward
10
Useful Commands
  • hostname Classroom_Switch


  • show ip


  • int vlan1


  • description This VLAN is for the classroom


  • delete nvram


  • copy running-config startup-config
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