VLAN Trunking Protocol 78

　　VTP Pruning 81

　　VTP Versions 82

　　VTP Versions 1 and 2 82

　　VTP Version 3 83

　　VTP Messages Types 83

　　Summary Advertisements 83

　　Subset Advertisements 84

　　Advertisement Requests 84

　　VTP Authentication 84

　　Best Practices for VTP Implementation 84

　　Configuring VTP 85

　　Verifying the VTP Configuration 85

　　Troubleshooting VTP 87

　　Private VLANs 87

　　Private VLANs Overview 88

　　Private VLANs and Port Types 88

　　Private VLAN Configuration 90

　　Configuring Private VLANs in Cisco IOS 91

　　Verifying Private VLAN 92

　　Private VLAN Configuration Example 93

　　Single Switch Private Configuration 93

　　Private VLAN Configuration Across Switches 94

　　Port Protected Feature 97

　　Configuring Link Aggregation with EtherChannel 97

　　Describe EtherChannel 98

　　PAgP and LACP Protocols 101

　　PAgP Modes 101

　　LACP Modes 103

　　Configure Port Channels Using EtherChannel 105

　　Guidelines for Configuring EtherChannel 105

　　Layer 2 EtherChannel Configuration Steps 106

　　Verifying EtherChannel 108

　　EtherChannel Load Balancing Options 110

　　Summary 112

　　Review Questions 113

　　Chapter 3 Implementing Spanning Tree 119

　　Evolution of Spanning Tree Protocols 119

　　Spanning Tree Protocol Basics 121

　　STP Operation 122

　　Rapid Spanning Tree Protocol 125

　　RSTP Port States 126

　　RSTP Port Roles 127

　　Rapid Transition to Forwarding 129

　　RSTP Topology Change Mechanism 132

　　Bridge Identifier for PVRST+ 136

　　Compatibility with 802.1D 137

　　Cisco Spanning Tree Default Configuration 137

　　PortFast 138

　　Configuring the PortFast Feature 138

　　Configuring the Basic Parameters of PVRST+ 140

　　Multiple Spanning Tree 141

　　MST Regions 143

　　Extended System ID for MST 144

　　Configuring MST 145

　　Spanning Tree Enhancements 150

　　BPDU Guard 152

　　BPDU Filtering 153

　　Root Guard 155

　　Preventing Forwarding Loops and Black Holes 158

　　Loop Guard 158

　　UDLD 161

　　Comparison Between Aggressive Mode UDLD and Loop Guard 165

　　Flex Links 166

　　Recommended Spanning Tree Practices 168

　　Troubleshooting STP 171

　　Potential STP Problems 171

　　Duplex Mismatch 172

　　Unidirectional Link Failure 172

　　Frame Corruption 173

　　Resource Errors 173

　　PortFast Configuration Error 174

　　Troubleshooting Methodology 174

　　Develop a Plan 175

　　Isolate the Cause and Correct an STP Problem 175

　　Document Findings 177

　　Summary 178

　　References 179

　　Review Questions 179