IP Networking. Cisco Press. Wendell Odom, CCIE No Indianapolis, IN East 96th Street

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1 IP Networking Wendell Odom, CCIE No Cisco Press 800 East 96th Street Indianapolis, IN 46240

2 iv IP Networking Contents at a Glance Introduction xxx Unit 1: The TCP/IP Model, LANs, WANs, and IP Networks Chapter 1 The TCP/IP and OSI Networking Models 3 Chapter 2 LAN Fundamentals 29 Chapter 3 WAN Fundamentals 57 Chapter 4 Class A, B, and C Networks 77 Unit 2: TCP/IP Network, Transport, and Application Layers Chapter 5 Fundamentals of IP Addressing and Routing 93 Chapter 6 Fundamentals of TCP/IP Transport, Applications, and Security 127 Chapter 7 Operating Cisco Routers 159 Unit 3: IP Subnetting and Basic Router Configuration Chapter 8 IP Subnetting 187 Chapter 9 Subnet Mask Conversion 209 Chapter 10 Analyzing Existing Subnet Masks 221 Chapter 11 Cisco Router Configuration 233 Unit 4: IP Routing with Connected, Static, and RIP-2 Routes Chapter 12 IP Routing: Static and Connected Routes 273 Chapter 13 Analyzing Existing Subnets 307 Chapter 14 Routing Protocol Concepts and RIP-2 Configuration 333 Unit 5: IP Troubleshooting and EIGRP Chapter 15 Troubleshooting IP Routing 357 Chapter 16 EIGRP Concepts and Configuration 393

3 Unit 6: Subnet Design Chapter 17 Subnet Mask Design 421 Chapter 18 Finding All Subnet IDs 435 Unit 7: Advanced IP Routing Topics and OSPF Chapter 19 VLSM and Route Summarization 453 Chapter 20 Troubleshooting IP Routing II 477 Chapter 21 OSPF Concepts and Configuration 505 Unit 8: Advanced IP Topics Chapter 22 Troubleshooting EIGRP and OSPF 541 Chapter 23 IP Version Unit 9: LANs Chapter 24 Ethernet LAN Switch Concepts 599 Chapter 25 Ethernet Switch Configuration 623 Chapter 26 Virtual LANs 643 Unit 10: WANs Chapter 27 Point-to-Point WANs 689 Chapter 28 Frame Relay Concepts 713 Chapter 29 Frame Relay Configuration 735 Appendixes Appendix A: Numeric Reference Tables 773 Appendix B: IP Access Control Lists 781 Glossary 811 Index 842

4 IP Networking Table of Contents Introduction xxx Unit 1: The TCP/IP Model, LANs, WANs, and IP Networks Chapter 1 The TCP/IP and OSI Networking Models 3 TCP/IP Networking Model 3 The History Leading to TCP/IP 4 Overview of the TCP/IP Networking Model 5 The TCP/IP Application Layer 7 HTTP Overview 7 HTTP Protocol Mechanisms 7 The TCP/IP Transport Layer 8 TCP Error Recovery Basics 9 Same Layer and Adjacent Layer Interactions 10 The TCP/IP Internet Layer 10 Internet Protocol (IP) and the Postal Service 11 Internet Protocol (IP) Addressing Basics 12 IP Routing Basics 13 The TCP/IP Network Access Layer 14 TCP/IP Model and Terminology 16 Comparing the Two TCP/IP Models 16 Data Encapsulation Terminology 16 Names of TCP/IP Messages 17 OSI Networking Model 18 Comparing OSI and TCP/IP 18 Describing Protocols by Referencing the OSI Layers OSI Layers and Their Functions 20 OSI Layering Concepts and Benefits 21 OSI Encapsulation Terminology 22 Chapter Review 24 Review Key Topics 24 Define Key Terms 24 Answer Review Questions 25

5 vii Chapter 2 LAN Fundamentals 29 An Overview of Modern Ethernet LANs 29 A Brief History of Ethernet 32 The Original Ethernet Standards: 10BASE2 and 10BASE5 32 Repeaters 33 Building 10BASE-T Networks with Hubs 34 Ethernet UTP Cabling 35 UTP Cables and RJ-45 Connectors 36 Transmitting Data Using Twisted Pairs 38 UTP Cabling Pinouts for 10BASE-T and 100BASE-TX BASE-T Cabling 41 Improving Performance by Using Switches Instead of Hubs 41 Increasing Available Bandwidth Using Switches 43 Doubling Performance by Using Full-Duplex Ethernet 45 Ethernet Layer 1 Summary 46 Ethernet Data-Link Protocols 46 Ethernet Addressing 46 Ethernet Framing 48 Identifying the Data Inside an Ethernet Frame 50 Error Detection 51 Chapter Review 52 Review Key Topics 52 Define Key Terms 52 Answer Review Questions 53 Chapter 3 WAN Fundamentals 57 OSI Layer 1 for Point-to-Point WANs 57 WAN Connections from the Customer Viewpoint 59 WAN Cabling Standards 61 Clock Rates, Synchronization, DCE, and DTE 62 Building a WAN Link in a Lab 63 Link Speeds Offered by Telcos 64 OSI Layer 2 for Point-to-Point WANs 65 HDLC 65 Point-to-Point Protocol 66 Point-to-Point WAN Summary 67

6 IP Networking Frame Relay and Packet-Switching Services 68 The Scaling Benefits of Packet Switching 68 Frame Relay Basics 69 Chapter Review 73 Review Key Topics 73 Define Key Terms 73 Answer Review Questions 73 Chapter 4 Class A, B, and C Networks 77 Classful Network Concepts 77 IPv4 Network Classes and Related Facts 77 Actual Class A, B, and C Networks 78 Address Formats 79 Default Masks 80 Number of Hosts per Network 81 Deriving the Network ID and Related Numbers 81 Unusual Network IDs and Network Broadcast Addresses 83 Practice with Classful Networks 84 Practice Deriving Key Facts Based on an IP Address 84 Practice Remembering the Details of Address Classes 85 Additional Practice 86 Chapter Review 87 Review Key Topics 87 Define Key Terms 87 Practice 87 Review Answers to Earlier Practice Problems 87 Answers to Practice Problem 7 88 Answers to Practice Problem 8 89 Answers to Practice Problem 9 89 Answer Review Questions 89 Unit 2: TCP/IP Network, Transport, and Application Layers Chapter 5 Fundamentals of IP Addressing and Routing 93 Overview of Network Layer Functions 94 Routing (Forwarding) 94 PCl's Logic: Sending Data to a Nearby Router 94 Rl's and R2's Logic: Routing Data Across the Network 95 R3's Logic: Delivering Data to the End Destination 96

7 ix Network Layer Interaction with the Data Link Layer 96 IP Packets and the IP Header 96 Network Layer (Layer 3) Addressing 98 Routing Protocols 99 IP Addressing 100 IP Addressing Definitions 100 How IP Addresses Are Grouped 101 Classes of Networks 102 The Actual Class A, B, and C Network Numbers 104 IP Subnetting 105 IP Routing 108 Host Routing 108 Router Forwarding Decisions and the IP Routing Table 110 IP Routing Protocols 112 Network Layer Utilities 114 Address Resolution Protocol and the Domain Name System 115 DNS Name Resolution 115 The ARP Process 116 Address Assignment and DHCP 117 ICMP Echo and the ping Command 119 Chapter Review 120 Review Key Topics 120 Define Key Terms 121 Answer Review Questions 121 Chapter 6 Fundamentals of TCP/IP Transport, Applications, and Security 127 TCP/IP Layer 4 Protocols: TCP and UDP 127 Transmission Control Protocol 128 Multiplexing Using TCP Port Numbers 128 Popular TCP/IP Applications and Application Layer Protocols 132 Error Recovery (Reliability) 133 Flow Control Using Windowing 134 Connection Establishment and Termination 135 Data Segmentation and Ordered Data Transfer 137 User Datagram Protocol 138 TCP/IP Applications 139 QoS Needs and the Impact of TCP/IP Applications 139

8 x IP Networking The World Wide Web, HTTP, and SSL 141 Universal Resource Locators 142 Finding the Web Server Using DNS 142 Transferring Files with HTTP 144 Network Security 144 Perspectives on the Sources and Types of Threats 145 Firewalls and the Cisco Adaptive Security Appliance (ASA) 149 Anti-x 151 Intrusion Detection and Prevention 151 Virtual Private Networks (VPN) 152 Chapter Review 154 Review Key Topics 154 Define Key Terms 154 Answer Review Questions 155 Chapter 7 Operating Cisco Routers 159 Installing Cisco Routers 159 Installing Enterprise Routers 160 Cisco Integrated Services Routers 161 Physical Installation 162 Installing Internet Access Routers 163 A SOHO Installation with a Separate Switch, Router, and Cable Modem 163 A SOHO Installation with an Integrated Switch, Router, and DSL Modem 164 Regarding the SOHO Devices Used in This Book 165 Accessing and Using the Cisco Router CLI 165 Accessing the CLI 165 CLI Accessfrom the Console 166 Accessing the CLI with Telnet and SSH 168 Password Security for CLI Access 169 User and Enable (Privileged) Modes 170 CLI Help Features 171 The debug and show Commands 173 Configuring Cisco IOS Software 174 Configuration Submodes and Contexts 174 Storing Router Configuration Files 176 Copying and Erasing Configuration Files 179 Chapter Review 181

9 xi Review Key Topics 181 Define Key Terms 181 Review Command References 181 Answer Review Questions 183 Unit 3: IP Subnetting and Basic Router Configuration Chapter 8 IP Subnetting 187 Analyze Needs 188 Rules About Which Hosts Are in Which Subnet 188 Determining the Number of Subnets 189 Determining the Number of Hosts per Subnet 190 One Size Subnet Fits All or Not 191 Defining the Size of a Subnet 191 One Size Subnet Fits All 192 Multiple Subnet Sizes (Variable-Length Subnet Masks) 193 This Book: One Size Subnet Fits All 194 Make Design Choices 194 Choose a Classful Network 194 Public IP Networks 195 Growth Exhausts the Public IP Address Space 196 Private IP Networks 197 Choosing an IP Network During the Design Phase 197 Choose the Mask 198 IP Networks Before Subnetting 198 Borrowing Host Bits to Create Subnet Bits 199 Choosing Enough Subnet and Host Bits 200 Example Design: ,200 Subnets, and 200 Hosts 201 Masks and Mask Formats 202 Build a List of All Subnets 203 Plan the Implementation 204 Chapter Review 205 Review Key Topics 205 Define Key Terms 205 Answer Review Questions 205 Chapter 9 Subnet Mask Conversion 209 Subnet Mask Conversion 209 The Three Mask Formats 209 Converting Between Binary and Prefix Masks 210

10 xii IP Networking Converting Between Binary and DDN Masks 211 Converting Between Prefix and DDN Masks 213 Practice Converting Subnet Masks 214 Practice Problems for This Chapter 214 Additional Practice 215 Chapter Review 216 Review Key Topics 216 Define Key Terms 216 Practice 216 Review Answers to Earlier Practice Problems 216 Answer Review Questions 217 Chapter 10 Analyzing Existing Subnet Masks 221 Defining the Format of IPv4 Addresses 221 Masks Divide the Subnet's Addresses into Two Parts 222 Masks and Class Divide Addresses into Three Parts 222 Classless and Classful Addressing 223 Calculations Based on the IPv4 Address Format 224 Practice Analyzing Subnet Masks 226 Practice Problems for This Chapter 226 Additional Practice 227 Chapter Review 228 Review Key Topics 228 Define Key Terms 228 Practice 228 Review Answers to Earlier Practice Problems 228 Answer Review Questions 230 Chapter 11 Cisco Router Configuration 233 Configuration Features in Common with Switches 233 Securing the Router CLI 233 Configuring Simple Password Security 234 Configuring Usernames and Secure Shell (SSH) 237 Password Encryption 240 The Two Enable Mode Passwords 241 Console and vty Settings 242 Banners 243 History Buffer Commands 244 The logging synchronous and exec-timeout Commands 244

11 xiii Configuring Features Specific to Cisco Routers 245 Router Interfaces 245 Interface Status Codes 247 Router Interface IP Addresses 248 Bandwidth and Clock Rate on Serial Interfaces 249 Router Auxiliary (Aux) Port 251 Initial Configuration (Setup Mode) 251 Upgrading Cisco IOS Software and the Cisco IOS Software Boot Process 254 Upgrading a Cisco IOS Software Image into Flash Memory 255 The Cisco IOS Software Boot Sequence 257 The Three Router Operating Systems 259 The Configuration Register 259 How a Router Chooses Which OS to Load 260 The show version Command and Seeing the Configuration Register's Value 262 Chapter Review 264 Review Key Topics 264 Define Key Terms 264 Review Command References to Check Your Memory 265 Answer Review Questions 268 Unit 4: IP Routing with Connected, Static, and RIP-2 Routes Chapter 12 IP Routing: Static and Connected Routes 273 IP Routing and Addressing 273 IP Routing 274 The Impact of Addressing and Subnetting on Routing 277 IP Forwarding by Matching the Most Specific Route 279 Routes to Directly Connected Subnets 280 Connected Routes 281 Secondary IP Addressing 284 Supporting Connected Routes to Subnet Zero 286 ISL and 802.1Q Configuration on Routers 287 Static Routes 289 Configuring Static Routes 291 The Extended ping Command 292 Static Default Routes 294 Default Routes Using the ip route Command 295 Default Routes Using the ip default-network Command 296

12 xiv IP Networking Default Route Summary 297 Classful and Classless Routing 298 Summary of the Use of the Terms Classless and Classful 298 Classless and Classful Routing Compared 299 Chapter Review 302 Review Key Topics 302 Define Key Terms 302 Review Command Reference to Check Your Memory 302 Answer Review Questions 304 Chapter 13 Analyzing Existing Subnets 307 Defining a Subnet 307 An Example with Network and Four Subnets 308 Subnet ID Concepts 309 The Subnet Broadcast Address 310 The Range of Usable Addresses 311 Analyzing Existing Subnets: Binary 311 Finding the Subnet ID Binary 312 Finding the Subnet Broadcast Binary 314 Binary Practice Problems 314 A Shortcut for the Binary Process 316 Brief Note About Boolean Math 317 Finding the Range of Addresses 318 Analyzing Existing Subnets: Decimal 318 Analysis with Easy Masks 318 Predictability in the Interesting Octet 319 Finding the Subnet ID: Difficult Masks 321 Resident Subnet Example Resident Subnet Example Resident Subnet Practice Problems 323 Finding the Subnet Broadcast Address: Difficult Masks 323 Subnet Broadcast Example Subnet Broadcast Example Subnet Broadcast Address Practice Problems 325 Practice Analyzing Existing Subnets 325 A Choice: To Memorize or to Calculate 325 Practice Problems for This Chapter 326 Additional Practice 326 Chapter Review 327 Review Key Topics 327

13 XV Define Key Terms 327 Practice 327 Answers to Earlier Practice Problems 327 Answer Review Questions 330 Chapter 14 Routing Protocol Concepts and RIP-2 Configuration 333 Routing Protocol Overview 333 RIP-2 Basic Concepts 334 Comparing and Contrasting IP Routing Protocols 335 Interior and Exterior Routing Protocols 335 Routing Protocol Types/Algorithms 337 Metrics 337 Autosummarization and Manual Summarization 338 Classless and Classful Routing Protocols 338 Convergence 339 Miscellaneous Comparison Points 339 Summary of Interior Routing Protocols 339 Configuring and Verifying RIP RIP-2 Configuration 340 Sample RIP Configuration 341 RIP-2 Verification 342 Interpreting the Output of the show ip route Command 345 Administrative Distance 345 The show ip protocols Command 347 Examining RIP Messages with debug 348 Chapter Review 351 Review Key Topics 351 Define Key Terms 351 Review Command Reference to Check Your Memory 351 Answer Review Questions 353 Unit 5: IP Troubleshooting and EIGRP Chapter 15 Troubleshooting IP Routing 357 IP Troubleshooting Tips and Tools 357 IP Addressing 358 Avoiding Reserved IP Addresses 358 One Subnet, One Mask, for Each LAN 359 Summary of IP Addressing Tips 360

14 xvi IP Networking Host Networking Commands 360 Troubleshooting Host Routing Problems 363 Finding the Matching Route on a Router 365 Troubleshooting Commands 367 The show ip arp Command 367 The traceroute Command 367 Telnet and Suspend 369 A Routing Troubleshooting Scenario 372 Scenario Part A: Tasks and Questions 372 Scenario Part A: Answers 375 Scenario Part B: Analyze Scenario Part B: Answers 377 Scenario Part B: Question Scenario Part B: Question Scenario Part B: Question Scenario Part B: Question Scenario Part B: Question Scenario Part B: Question Scenario Part B: Question Packet/Frame Flow 377 Scenario Part C: Analyze Connected Routes 383 Scenario Part C: Answers 384 Chapter Review 386 Review Key Topics 386 Review Command Reference to Check Your Memory 387 Answer Review Questions 388 Chapter 16 EIGRP Concepts and Configuration 393 EIGRP Concepts and Operation 393 EIGRP Neighbors 394 Exchanging EIGRP Topology Information 394 Calculating the Best Routes for the Routing Table 395 Feasible Distance and Reported Distance 397 Caveats with Bandwidth on Serial Links 397 EIGRP Convergence 398 EIGRP Successors and Feasible Successors 398 The Query and Reply Process 400 EIGRP Summary and Comparisons with OSPF 400 EIGRP Configuration and Verification 401 Basic EIGRP Configuration 402

15 xvii EIGRP Metrics, Successors, and Feasible Successors 404 Creating and Viewing a Feasible Successor Route 406 Convergence Using the Feasible Successor Route 407 EIGRP Authentication 408 EIGRP Maximum Paths and Variance 411 Tuning the EIGRP Metric Calculation 412 Chapter Review 414 Review Key Topics 414 Define Key Terms 414 Review Command Reference to Check Your Memory 414 Answer Review Questions 417 Unit 6: Subnet Design Chapter 17 Subnet Mask Design 421 Choosing the Mask(s) to Meet Requirements 421 Review: Choosing the Minimum Number of Subnet and Host Bits 422 No Masks Meet Requirements 423 One Mask Meets Requirements 424 Multiple Masks Meet Requirements 425 Finding All the Masks: Concepts 425 Finding All the Masks: Math 426 Choosing the Best Mask 427 The Formal Process 427 Practice Choosing Subnet Masks 428 Practice Problems for This Chapter 429 Additional Practice 429 Chapter Review 430 Review Key Topics 430 Define Key Terms 430 Practice 430 Review Answers to Earlier Practice Problems 430 Answer Review Questions 431 Chapter 18 Finding All Subnet IDs 435 Finding All Subnet IDs 435 The First Subnet ID: The Zero Subnet 435 Finding the Pattern Using the Magic Number 436 A Formal Process, with Less Than 8 Subnet Bits 437 Example 1: Network , Mask Example 2: Network , Mask

16 xviii IP Networking Finding All Subnets with Exactly 8 Subnet Bits 440 Finding All Subnets with More Than 8 Subnet Bits 441 Process with 9-16 SubnetBits 442 Process with 17 or More Subnet Bits 443 Practice Finding All Subnet IDs 444 Practice Problems for This Chapter 445 Additional Practice 445 Chapter Review 446 Review Key Topics 446 Define Key Terms 446 Review Answers to Earlier Practice Problems 446 Answer, Practice Problem Answer, Practice Problem Answer, Practice Problem Answer Review Questions 449 Unit 7: Advanced IP Routing Topics and OSPF Chapter 19 VLSM and Route Summarization 453 VLSM 453 Classless and Classful Routing Protocols 454 Overlapping VLSM Subnets 455 Designing a Subnetting Scheme Using VLSM 456 Adding a New Subnet to an Existing Design 459 VLSM Configuration 460 Manual Route Summarization 461 Route Summarization Concepts 461 Route Summarization Strategies 465 Sample "Best" Summary on Seville 466 Sample "Best" Summary on Yosemite 466 Autosummarization and Discontiguous Classful Networks 467 An Example of Autosummarization 468 Discontiguous Classful Networks 469 Autosummarization Support and Configuration 471 Chapter Review 473 Review Key Topics 473 Define Key Terms 473 Review Command Reference to Check Your Memory 473 Answer Review Questions 474

17 xix Chapter 20 Troubleshooting IP Routing II 477 The ping and traceroute Commands 477 Internet Control Message Protocol (ICMP) 477 The ping Command and the ICMP Echo Request and Echo Reply 478 The Destination Unreachable ICMP Message 478 The Redirect ICMP Message 481 The ICMP Time Exceeded Message 481 The traceroute Command 482 Troubleshooting the Packet Forwarding Process 485 Isolating IP Routing Problems Related to Hosts 485 Isolating IP Routing Problems Related to Routers 486 Troubleshooting Scenario 1: Forward Route Problem 488 Troubleshooting Scenario 2: Reverse Route Problem 491 An Alternative Problem Isolation Process for Steps 3, 4, and Troubleshooting Tools and Tips 494 Host Routing Tools and Perspectives 494 show ip route Reference 495 Interface Status 496 VLSM Issues 496 Recognizing When VLSM Is Used 497 Configuring Overlapping VLSM Subnets 497 Symptoms with Overlapping Subnets 499 VLSM Troubleshooting Summary 500 Discontiguous Networks and Autosummary 501 Chapter Review 502 Review Key Topics 502 Define Key Terms 502 Chapter 21 OSPF Concepts and Configuration 505 Link-State Routing Protocol Features 505 Building the Same LSDB on Every Router 505 Applying Dijkstra SPF Math to Find the Best Routes 507 Convergence with Link-Stare Protocols 509 Summary and Comparisons to Distance Vector Protocols 509 OSPF Protocols and Operation 510 OSPF Neighbors 511 Identifying OSPF Routers with a Router ID 511 Meeting Neighbors by Saying Hello 511

18 XX IP Networking Potential Problems in Becoming a Neighbor 512 Neighbor States 513 OSPF Topology Database Exchange 514 Overview of the OSPF Database Exchange Process 515 Choosing a Designated Router 515 Database Exchange 517 Mamtaining the LSDB While Being Fully Adjacent 517 Summary of Neighbor States 518 Building the IP Routing Table 518 Scaling OSPF Through Hierarchical Design 519 OSPF Areas 520 OSPF Area Design Advantages 522 OSPF Configuration 523 OSPF Single-Area Configuration 523 OSPF Configuration with Multiple Areas 525 Configuring the OSPF Router ID 527 OSPF Hello and Dead Timers 528 OSPF Metrics (Cost) 530 OSPF Authentication 531 OSPF Load Balancing 533 Chapter Review 534 Review Key Topics 534 Define Key Terms 534 Review Command Reference to Check Your Memory 535 Answer Review Questions 537 Unit 8: Advanced IP Topics Chapter 22 Troubleshooting EIGRP and OSPF 541 Perspectives on Troubleshooting Routing Protocol Problems 541 Interfaces Enabled with a Routing Protocol 542 EIGRP Interface Troubleshooting Example 543 OSPF Interface Troubleshooting Example 548 Neighbor Relationships 550 EIGRP Neighbor Requirements 551 OSPF Neighbor Requirements 553 OSPF Neighbor Example OSPF Neighbor Example The MTU Matching Requirement 558

19 xxi Chapter Review 559 Review Key Topics 559 Review Command Reference to Check Your Memory 559 Chapter 23 IP Version Global Unicast Addressing, Routing, and Subnetting 564 Global Route Aggregation for Efficient Routing 565 Conventions for Representing IPv6 Addresses 567 Conventions for Writing IPv6 Prefixes 568 Global Unicast Prefix Assignment Example 570 Subnetting Global Unicast IPv6 Addresses Inside an Enterprise 571 Prefix Terminology 574 IPv6 Protocols and Addressing 575 DHCP for IPv6 575 IPv6 Host Address Assignment 576 The IPv6 Interface ID and EUI-64 Format 576 Static IPv6 Address Configuration 577 Stateless Autoconfiguration and Router Advertisements 578 IPv6 Address Configuration Summary 580 Discovering the Default Router with NDP 580 Learning the IP Address(es) of DNS Servers 580 IPv6 Addresses 581 Unicast IPv6 Addresses 581 Multicast and Other Special IPv6 Addresses 583 Summary of IP Protocols and Addressing 584 Configuring IPv6 Routing and Routing Protocols 585 IPv6 Routing Protocols 585 IPv6 Configuration 586 IPv6 Transition Options 589 IPv4/IPv6 Dual Stacks 589 Tunneling 590 Translating Between IPv4 and IPv6 with NAT-PT 591 Transition Summary 592 Chapter Review 593 Review Key Topics 593 Define Key Terms 593 Review Command Reference to Check Your Memory 594 Answer Review Questions 595

20 xxii IP Networking Unit 9: LANs Chapter 24 Ethernet LAN Switch Concepts 599 LAN Switching Concepts 599 Historical Progression: Hubs, Bridges, and Switches 599 Switching Logic 602 The Forward Versus Filter Decision 603 How Switches Learn MAC Addresses 604 Flooding Frames 605 Avoiding Loops Using Spanning Tree Protocol 606 Internal Processing on Cisco Switches 607 LAN Switching Summary 609 LAN Design Considerations 610 Collision Domains and Broadcast Domains 610 Collision Domains 610 Broadcast Domains 611 The Impact of Collision and Broadcast Domains on LAN Design 612 Virtual LANs (VLAN) 613 Campus LAN Design Terminology 615 Ethernet LAN Media and Cable Lengths 617 Chapter Review 619 Review Key Topics 619 Define Key Terms 619 Answer Review Questions 620 Chapter 25 Ethernet Switch Configuration 623 Comparing Cisco Router and Switch Configuration 623 LAN Switch Configuration and Operation 624 Configuring the Switch IP Address 625 Configuring Switch Interfaces 627 Port Security 629 VLAN Configuration 632 Securing Unused Switch Interfaces 635 Chapter Review 636 Review Key Topics 636 Define Key Terms 636 Review Command Reference to Check Your Memory 637 Answer Review Questions 639

21 xxiii Chapter 26 Virtual LANs 643 Virtual LAN Concepts 643 Trunking with ISL and 802.1Q 644 ISL 646 IEEE 802.1Q 646 ISL and 802.1Q Compared 64 6 IP Subnets and VLANs 648 VLAN Trunking Protocol (VTP) 649 Normal VTP Operation Using VTP Server and Client Modes 650 Three Requirements for VTP to Work Between Two Switches 651 Avoiding VTP by Using VTP Transparent Mode 652 Storing VLAN Configuration 652 VTP Versions 653 VTP Pruning 654 Summary of VTP Features 654 VLAN and VLAN Trunking Configuration and Verification 655 Creating VLANs and Assigning Access VLANs to an Interface 655 VLAN Configuration Example 1: Full VLAN Configuration 656 VLAN Configuration Example 2: Shorter VLAN Configuration 659 VLAN Trunking Configuration 660 Controlling Which VLANs Can Be Supported on a Trunk 665 Trunking to Cisco IP Phones 667 Securing VLANs and Trunking 669 VTP Configuration and Verification 669 Using VTP: Configuring Servers and Clients 669 Caveats When Moving Away from Default VTP Configuration 673 Avoiding VTP: Configuring Transparent Mode 674 Troubleshooting VTP 675 Determining Why VTP Is Not Currently Working 675 Problems When Connecting New Switches and Bringing Up Trunks 680 Avoiding VTP Problems Through Best Practices 682 Chapter Review 683 Review Key Topics 683 Define Key Terms 684 Review Command Reference to Check Your Memory 684 Answer Review Questions 685

22 xxiv IP Networking Unit 10: WANs Chapter 27 Point-to-Point WANs 689 PPP Concepts 689 The PPP Protocol Field 689 PPP Link Control Protocol (LCP) 690 Looped Link Detection 691 Enhanced Error Detection 691 PPPMultilink 692 PPP Authentication 693 PPP Configuration 694 Basic PPP Configuration 694 CHAP Configuration and Verification 695 Configuring HDLC 696 Troubleshooting Serial Links 699 Troubleshooting Layer 1 Problems 700 Troubleshooting Layer 2 Problems 701 KeepaliveFailure 702 PAP and CHAP Authentication Failure 703 Troubleshooting Layer 3 Problems 704 Chapter Review 707 Review Key Topics 707 Define Key Terms 707 Command Reference to Check Your Memory 707 Answer Review Questions 708 Chapter 28 Frame Relay Concepts 713 Frame Relay Overview 713 Frame Relay Standards 715 Virtual Circuits 716 LMI and Encapsulation Types 718 Frame Relay Addressing 720 Frame Relay Local Addressing 721 Frame Relay Global Addressing 721 Network Layer Concerns with Frame Relay 724 Frame Relay Layer 3 Addressing: One Subnet Containing All Frame Relay DTEs 725 Frame Relay Layer 3 Addressing: One Subnet Per VC 725 Frame Relay Layer 3 Addressing: Hybrid Approach 727 Layer 3 Broadcast Handling 728

23 XXV Chapter Review 730 Review Key Topics 730 Define Key Terms 730 Answer Review Questions 731 Chapter 29 Frame Relay Configuration 735 Frame Relay Configuration and Verification 735 Planning a Frame Relay Configuration 735 A Fully Meshed Network with One IP Subnet 737 Configuring the Encapsulation and LMI 738 Frame Relay Address Mapping 740 Inverse ARP 742 Static Frame Relay Mapping 744 A Partially Meshed Network with One IP Subnet Per VC 745 Assigning a DLCI to a Particular Subinterface 747 Comments About Global and Local Addressing 748 Frame Relay Verification 748 A Partially Meshed Network with Some Fully Meshed Parts 750 Frame Relay Troubleshooting 754 A Suggested Frame Relay Troubleshooting Process 754 Layer 1 Issues on the Access Link (Step 1) 756 Layer 2 Issues on the Access Link (Step 2) 756 PVC Problems and Status (Step 3) 758 Find the Connected Subnetand Outgoing Interface (Steps 3a and 3b) 759 Find the PVCs Assigned to That Interface (Step 3c) 760 Determine Which PVC Is Used to Reach a Particular Neighbor (Step 3d) 761 PVC Status 762 Subinterface Status 763 Frame Relay Mapping Issues (Step 4) 764 End-to-End Encapsulation (Step 5) 765 Mismatched Subnet Numbers (Step 6) 766 Chapter Review 767 Review Key Topics 767 Review Command Reference to Check Your Memory 767 Answer Review Questions 769

24 xxvi IP Networking Appendixes Appendix A: Numeric Reference Tables 773 Appendix B: IP Access Control Lists 781 Glossary 811 Index 842