Introduction xxx Part I Fundamental Troubleshooting and Maintenance Concepts Chapter 1 Introduction to Troubleshooting and Network Maintenance 3 "Do I Know This Already?" Quiz 3 Foundation Topics 9 Introduction to Troubleshooting 9 Defining Troubleshooting 9 The Value of Structured Troubleshooting 11 A Structured Approach 13 1. Problem Report 13 2. Collect Information 14 3. Examine Collected Information 15 4. Eliminate Potential Causes 16 5. Propose an Hypothesis 17 6. Verify Hypothesis 18 7. Problem Resolution 19 Popular Troubleshooting Methods 20 The Top-Down Method 21 The Bottom-Up Method 21 The Divide-and-Conquer Method 22 The Following the Traffic Path Method 23 The Comparing Configurations Method 23 The Component Swapping Method 24 Practice Exercise: Selecting a Troubleshooting Approach 25 Introduction to Network Maintenance 26 Defining Network Maintenance 26 Proactive Versus Reactive Network Maintenance 27 Well-Known Network Maintenance Models 28 Example of Adapting a Network Maintenance Model 28 Common Maintenance Procedures 29 Routine Maintenance Tasks 29 Scheduled Maintenance 30 Managing Network Changes 30 Maintaining Network Documentation 32 Restoring Operations After a Failure 33 Measuring Network Performance 34 The Troubleshooting and Network Maintenance Relationship 34 Maintaining Current Network Documentation 35 Establishing a Baseline 36 Communication 36 Change Management 37 Exam Preparation Tasks 39 Review All Key Topics 39 Define Key Terms 39 Chapter 2 Troubleshooting and Maintenance Tools 41 "Do I Know This Already?" Quiz 41 Foundation Topics 45 The Troubleshooting and Network Maintenance Toolkit 45 Network Documentation Tools 46 Basic Tools 47 CLI Tools 47 GUI Tools 48 Recovery Tools 48 Logging Tools 53 Network Time Protocol as a Tool 56 Advanced Tools 57 Overview of SNMP and NetFlow 57 Creating a Baseline with SNMP and NetFlow 58 SNMP 58 NetFlow 59 Cisco Support Tools 64 Using Cisco IOS to Verify and Define the Problem 64 Ping 64 Telnet 67 Traceroute 67 Using Cisco IOS to Collect Information 68 Filtering the Output of show Commands 69 Redirecting show Command Output to a File 73 Troubleshooting Hardware 74 Collecting Information in Transit 75 Performing Packet Captures 75 SPAN 76 RSPAN 78 Using Tools to Document a Network 80 Exam Preparation Tasks 85 Review All Key Topics 85 Define Key Terms 86 Complete Tables and Lists from Memory 86 Command Reference to Check Your Memory 86 Chapter 3 Troubleshooting Device Performance 93 "Do I Know This Already?" Quiz 93 Foundation Topics 96 Troubleshooting Switch Performance Issues 96 Cisco Catalyst Switch Troubleshooting Targets 96 TCAM Troubleshooting 101 High CPU Utilization Troubleshooting on a Switch 105 Troubleshooting Router Performance Issues 106 Excessive CPU Utilization 107 Understanding Packet-Switching Modes (Routers and Multilayer Switches) 113 Troubleshooting Packet-Switching Modes 116 Excessive Memory Utilization 121 Exam Preparation Tasks 124 Review All Key Topics 124 Define Key Terms 124 Complete Tables and Lists from Memory 125 Command Reference to Check Your Memory 125 Part II Troubleshooting Cisco Catalyst Switch Features Chapter 4 Troubleshooting Layer 2 Trunks, VTP, and VLANs 129 "Do I Know This Already?" Quiz 129 Foundation Topics 132 Frame-Forwarding Process 132 Troubleshooting Trunks 140 Encapsulation Mismatch 141 Incompatible Trunking Modes 143 VTP Domain Name Mismatch 146 Native VLAN Mismatch 146 Allowed VLANs 147 Troubleshooting VTP 148 Domain Name Mismatch 148 Version Mismatch 149 Mode Mismatch 149 Password Mismatch 151 Higher Revision Number 151 Troubleshooting VLANs 152 Incorrect IP Addressing 152 Missing VLAN 153 Incorrect Port Assignment 154 The MAC Address Table 155 Layer 2 Trouble Tickets 157 Trouble Ticket 4-1 158 Trouble Ticket 4-2 160 Exam Preparation Tasks 165 Review All Key Topics 165 Define Key Terms 165 Complete Tables and Lists from Memory 166 Command Reference to Check Your Memory 166 Chapter 5 Troubleshooting STP and Layer 2 EtherChannel 169 "Do I Know This Already?" Quiz 169 Foundation Topics 172 Spanning Tree Protocol Overview 172 Reviewing STP Operation 173 Determining Root Port 175 Determining Designated Port 176 Determining Nondesignated Port 176 Collecting Information About an STP Topology 177 Gathering STP Information 177 Gathering MSTP Information 179 STP Troubleshooting Issues 180 Corruption of a Switch''s MAC Address Table 180 Broadcast Storms 181 Troubleshooting STP Features 182 PortFast 183 BPDU Guard 184 BPDU Filter 187 Root Guard 189 Loop Guard 190 STP Trouble Tickets 190 Trouble Ticket 5-1 191 Trouble Ticket 5-2 194 Trouble Ticket 5-3 196 Troubleshooting Layer 2 EtherChannel 199 Reviewing Layer 2 EtherChannel 199 EtherChannel Trouble Tickets 200 Trouble Ticket 5-4 201 Trouble Ticket 5-5 204 Exam Preparation Tasks 206 Review All Key Topics 206 Define Key Terms 206 Complete Tables and Lists from Memory 207 Command Reference to Check Your Memory 207 Chapter 6 Troubleshooting Inter-VLAN Routing and Layer 3 EtherChannels 209 "Do I Know This Already?" Quiz 209 Foundation Topics 212 Troubleshooting a Router-on-a-Trunk/Stick 212 Router-on-a-Trunk/Stick Trouble Tickets 213 Trouble Ticket 6-1 214 Trouble Ticket 6-2 218 Troubleshooting Switched Virtual Interfaces 221 Reviewing SVIs 221 Troubleshooting SVIs 223 SVI Trouble Tickets 224 Trouble Ticket 6-3 225 Trouble Ticket 6-4 230 Troubleshooting Routed Ports 233 Routed Ports Trouble Tickets 234 Trouble Ticket 6-5 235 Troubleshooting Layer 3 EtherChannel 237 Layer 3 EtherChannel Trouble Tickets 239 Trouble Ticket 6-6 240 Exam Preparation Tasks 244 Review All Key Topics 244 Define Key Terms 244 Complete Tables and Lists from Memory 245 Show Command Reference to Check Your Memory 245 Chapter 7 Troubleshooting Switch Security Features 247 "Do I Know This Already?" Quiz 247 Foundation Topics 250 Troubleshooting Port Security 250 Common Port Security Issues 250 Port Security Configured but Not Enabled 250 Static MAC Address Not Configured Correctly 251 Maximum Number of MAC Addresses Reached 253 Legitimate Users Being Blocked Because of Violation 254 Running Configuration Not Saved to Startup Configuration 260 Port Security Trouble Tickets 261 Trouble Ticket 7-1 261 Troubleshooting Spoof-Prevention Features 265 DHCP Snooping 265 Dynamic ARP Inspection 267 IP Source Guard 268 Spoof-Prevention Features Trouble Tickets 270 Trouble Ticket 7-2 270 Troubleshooting Access Control 273 Protected Ports 273 Private VLANs 275 VACLs 279 Exam Preparation Tasks 281 Review All Key Topics 281 Define Key Terms 282 Command Reference to Check Your Memory 282 Chapter 8 Troubleshooting First-Hop Redundancy Protocols 287 "Do I Know This Already?" Quiz 287 Foundation Topics 290 Troubleshooting HSRP 290 Reviewing HSRP 290 HSRP Converging After a Failure 291 HSRP Verification and Troubleshooting 292 Virtual Router MAC Address 293 Interface Tracking 293 Verifying First Hop 294 Debug 296 HSRP Trouble Tickets 297 Trouble Ticket 8-1 297 Trouble Ticket 8-2 300 Trouble Ticket 8-3 302 Troubleshooting VRRP 306 Reviewing VRRP 306 VRRP Verification and Troubleshooting 308 Virtual Router MAC Address 309 Object Tracking 309 Verifying First Hop 310 VRRP Trouble Tickets 312 Trouble Ticket 8-4 312 Trouble Ticket 8-5 315 Troubleshooting GLBP 318 Reviewing GLBP 319 GLBP Verification and Troubleshooting 321 Virtual Router MAC Addresses 323 GLBP Object Tracking 323 Verifying GLBP First Hop 325 GLBP Trouble Tickets 326 Trouble Ticket 8-6 327 Trouble Ticket 8-7 329 Comparing HSRP, VRRP, and GLBP 330 Exam Preparation Tasks 332 Review All Key Topics 332 Define Key Terms 333 Complete Tables and Lists from Memory 333 Command Reference to Check Your Memory 333 Part III Troubleshooting Router Features Chapter 9 Troubleshooting IPv4 Addressing and Addressing Technologies 335 "Do I Know This Already?" Quiz 335 Foundation Topics 338 Troubleshooting IPv4 Addressing 338 IPv4 Addressing Issues 338 Determining IP Addresses Within a Subnet 341 Troubleshooting DHCP for IPv4 342 Reviewing DHCP Operations 342 Potential DHCP Troubleshooting Issues 347 DHCP Troubleshooting Commands 348 Troubleshooting NAT 350 Reviewing NAT 350.