Ethernet Switches

1. Basic Switch Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
What an Ethernet Switch Does 1
Bridges and Switches 1
What Is a Switch? 2
Operation of Ethernet Switches 3
Transparent Bridging 4
Address Learning 4
Traffic Filtering 6
Frame Flooding 7
Broadcast and Multicast Traffic 7
Combining Switches 9
Forwarding Loops 9
Spanning Tree Protocol 10
Spanning Tree Packets 11
Choosing a Root Bridge 11
Choosing the Least-Cost Path 11
Blocking Loop Paths 12
Spanning Tree Port States 13
Spanning Tree Versions 15
Switch Performance Issues 16
Packet Forwarding Performance 17
Switch Port Memory 17
Switch CPU and RAM 18
Switch Specifications 18
2. Basic Switch Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Switch Management 23

Simple Network Management Protocol 24
Packet Mirror Ports 24
Switch Traffic Filters 24
Virtual LANs 26
802.1Q VLAN Standard 27
Linking VLANs 27
802.1Q Multiple Spanning Tree Protocol 28
Quality of Service (QoS) 28
3. Network Design with Ethernet Switches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Advantages of Switches in Network Designs 29
Improved Network Performance 29
Switch Hierarchy and Uplink Speeds 31
Uplink Speeds and Traffic Congestion 32
Multiple Conversations 33
Switch Traffic Bottlenecks 34
Hierarchical Network Design 35
Seven Hop Maximum 37
Network Resiliency with Switches 38
Spanning Tree and Network Resiliency 38
Routers 40
Operation and Use of Routers 41
Routers or Bridges? 42
4. Special-Purpose Switches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Multilayer Switches 45
Access Switches 46
Stacking Switches 46
Industrial Ethernet 47
Wireless Access Point Switches 48
Internet Service Provider Switches 48
Metro Ethernet 49
Data Center Switches 49
Data Center Port Speeds 50
Data Center Switch Types 50
Data Center Oversubscription 50
Data Center Switch Fabrics 51
Data Center Switch Resiliency 52
5. Advanced Switch Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Traffic Flow Monitoring 53
sFlow and Netflow 53