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Contents

Introduction xxxi Chapter 1 Single-Area OSPFv2 Concepts 1 Objectives 1 Key Terms 1 Introduction (1.0) 3 OSPF Features and Characteristics (1.1) 3 Introduction to OSPF (1.1.1) 3 Components of OSPF (1.1.2) 4 Routing Protocol Messages 4 Data Structures 4 Algorithm 5 Link-State Operation (1.1.3) 6 1. Establish Neighbor Adjacencies 6 2. Exchange Link-State Advertisements 6 3. Build the Link-State Database 7 4. Execute the SPF Algorithm 8 5. Choose the Best Route 8 Single-Area and Multiarea OSPF (1.1.4) 9 Multiarea OSPF (1.1.5) 10 OSPFv3 (1.1.6) 12 OSPF Packets (1.2) 13 Types of OSPF Packets (1.2.2) 13 Link-State Updates (1.2.3) 14 Hello Packet (1.2.4) 15 OSPF Operation (1.3) 17 OSPF Operational States (1.3.2) 17 Establish Neighbor Adjacencies (1.3.3) 18 1. Down State to Init State 18 2. The Init State 19 3. Two-Way State 19 4. Elect the DR and BDR 20 Synchronizing OSPF Databases (1.3.4) 20 1. Decide First Router 21 2. Exchange DBDs 21 3. Send an LSR 22 The Need for a DR (1.3.5) 23 LSA Flooding with a DR (1.3.6) 24 Flooding LSAs 24 LSAs and DR 25 Summary (1.4) 27 OSPF Features and Characteristics 27 OSPF Packets 28 OSPF Operation 28 Practice 29 Check Your Understanding 29 Chapter 2 Single-Area OSPFv2 Configuration 33 Objectives 33 Key Terms 33 Introduction (2.0) 34 OSPF Router ID (2.1) 34 OSPF Reference Topology (2.1.1) 34 Router Configuration Mode for OSPF (2.1.2) 35 Router IDs (2.1.3) 36 Router ID Order of Precedence (2.1.4) 36 Configure a Loopback Interface as the Router ID (2.1.5) 37 Explicitly Configure a Router ID (2.1.6) 38 Modify a Router ID (2.1.7) 39 Point-to-Point OSPF Networks (2.2) 40 The network Command Syntax (2.2.1) 40 The Wildcard Mask (2.2.2) 41 Configure OSPF Using the network Command (2.2.4) 41 Configure OSPF Using the ip ospf Command (2.2.6) 43 Passive Interface (2.2.8) 44 Configure Passive Interfaces (2.2.9) 45 OSPF Point-to-Point Networks (2.2.11) 46 Loopbacks and Point-to-Point Networks (2.2.12) 48 Multiaccess OSPF Networks (2.3) 49 OSPF Network Types (2.3.1) 49 OSPF Designated Router (2.3.2) 49 OSPF Multiaccess Reference Topology (2.3.3) 51 Verify OSPF Router Roles (2.3.4) 52 R1 DROTHER 52 R2 BDR 53 R3 DR 53 Verify DR/BDR Adjacencies (2.3.5) 54 R1 Adjacencies 55 R2 Adjacencies 55 R3 Adjacencies 56 Default DR/BDR Election Process (2.3.6) 56 DR Failure and Recovery (2.3.7) 58 R3 Fails 58 R3 Rejoins Network 59 R4 Joins Network 59 R2 Fails 59 The ip ospf priority Command (2.3.8) 61 Configure OSPF Priority (2.3.9) 61 Modify Single-Area OSPFv2 (2.4) 63 Cisco OSPF Cost Metric (2.4.1) 63 Adjust the Reference Bandwidth (2.4.2) 64 OSPF Accumulates Costs (2.4.3) 66 Manually Set OSPF Cost Value (2.4.4) 67 Test Failover to Backup Route (2.4.5) 69 Hello Packet Intervals (2.4.7) 69 Verify Hello and Dead Intervals (2.4.8) 70 Modify OSPFv2 Intervals (2.4.9) 71 Default Route Propagation (2.5) 73 Propagate a Default Static Route in OSPFv2 (2.5.1) 74 Verify the Propagated Default Route (2.5.2) 75 Verify Single-Area OSPFv2 (2.6) 77 Verify OSPF Neighbors (2.6.1) 77 Verify OSPF Protocol Settings (2.6.2) 79 Verify OSPF Process Information (2.6.3) 80 Verify OSPF Interface Settings (2.6.4) 81 Summary (2.7) 83 OSPF Router ID 83 Point-to-Point OSPF Networks 83 OSPF Network Types 84 Modify Single-Area OSPFv2 85 Default Route Propagation 86 Verify Single-Area OSPFv2 86 Practice 87 Check Your Understanding 88 Chapter 3 Network Security Concepts 93 Objectives 93 Key Terms 93 Introduction 95 Ethical Hacking Statement (3.0.3) 95 Current State of Cybersecurity (3.1) 95 Current State of Affairs (3.1.1) 95 Vectors of Network Attacks (3.1.2) 96 Data Loss (3.1.3) 97 Threat Actors (3.2) 98 The Hacker (3.2.1) 98 Evolution of Hackers (3.2.2) 99 Cyber Criminals (3.2.3) 100 Hacktivists (3.2.4) 100 State-Sponsored Hackers (3.2.5) 100 Threat Actor Tools (3.3) 101 Introduction to Attack Tools (3.3.2) 101 Evolution of Security Tools (3.3.3) 102 Attack Types (3.3.4) 104 Malware (3.4) 106 Overview of Malware (3.4.1) 106 Viruses and Trojan Horses (3.4.2) 106 Other Types of Malware (3.4.3) 108 Common Network Attacks (3.5) 109 Overview of Network Attacks (3.5.1) 109 Reconnaissance Attacks (3.5.3) 109 Access Attacks (3.5.5) 110 Trust Exploitation Example 111 Port Redirection Example 112 Man-in-the-Middle Attack Example 112 Buffer Overflow Attack 112 Social Engineering Attacks (3.5.6) 114 DoS and DDoS Attacks (3.5.9) 115 DoS Attack 116 DDoS Attack 116 IP Vulnerabilities and Threats (3.6) 117 IPv4 and IPv6 (3.6.2) 118 ICMP Attacks (3.6.3) 118 Amplification and Reflection Attacks (3.6.5) 119 Address Spoofing Attacks (3.6.6) 120 TCP and UDP Vulnerabilities (3.7) 122 TCP Segment Header (3.7.1) 122 TCP Services (3.7.2) 123 TCP Attacks (3.7.3) 124 TCP SYN Flood Attack 124 TCP Reset Attack 125 TCP Session Hijacking 126 UDP Segment Header and Operation (3.7.4) 126 UDP Attacks (3.7.5) 127 UDP Flood Attacks 127 IP Services 127 ARP Vulnerabilities (3.8.1) 127 ARP Cache Poisoning (3.8.2) 128 ARP Request 128 ARP Reply 129 Spoofed Gratuitous ARP Replies 130 DNS Attacks (3.8.4) 131 DNS Open Resolver Attacks 131 DNS Stealth Attacks 132 DNS Domain Shadowing Attacks 132 DNS Tunneling (3.8.5) 132 DHCP (3.8.6) 133 DHCP Attacks (3.8.7) 134 1. Client Broadcasts DHCP Discovery Messages 134 2. DHCP Servers Respond with Offers 134 3. Client Accepts Rogue DHCP Request 136 4. Rogue DHCP Acknowledges the Request 136 Network Security Best Practices (3.9) 137 Confidentiality, Integrity, and Availability (3.9.1) 137 The Defense-in-Depth Approach (3.9.2) 138 Firewalls (3.9.3) 139 IPS (3.9.4) 140 Content Security Appliances (3.9.5) 141 Cisco Email Security Appliance (ESA) 142 Cisco Web Security Appliance (WSA) 142 Cryptography (3.10) 143 Securing Communications (3.10.2) 143 Data Integrity (3.10.3) 144 Hash Functions (3.10.4) 145 MD5 with 128-Bit Digest 145 SHA Hashing Algorithm 146 SHA-2 146 SHA-3 146 Origin Authentication (3.10.5) 147 HMAC Hashing Algorithm 147 Creating the HMAC Value 148 Verifying the HMAC Value 149 Cisco Router HMAC Example 149 Data Confidentiality (3.10.6) 150 Symmetric Encryption (3.10.7) 151 Asymmetric Encryption (3.10.8) 152 Diffie-Hellman (3.10.9) 155 Summary (3.11) 157 Current State of Cybersecurity 157 Threat Actors 157 Threat Actor Tools 157 Malware 157 Common Network Attacks 158 IP Vulnerabilities and Threats 158 TCP and UDP Vulnerabilities 158 IP Services 158 Network Security Best Practices 159 Cryptography 159 Practice 159 Check Your Understanding 160 Chapter 4 ACL Concepts 163 Objectives 163 Key Terms 163 Introduction (4.0) 164 Purpose of ACLs (4.1) 164 What Is an ACL? (4.1.1) 164 Packet Filtering (4.1.2) 165 ACL Operation (4.1.3) 166 Wildcard Masks in ACLs (4.2) 168 Wildcard Mask Overview (4.2.1) 168 Wildcard Mask Types (4.2.2) 169 Wildcard to Match a Host 169 Wildcard Mask to Match an IPv4 Subnet 169 Wildcard Mask to Match an IPv4 Address Range 170 Wildcard Mask Calculation (4.2.3) 170 Example 1 171 Example 2 171 Example 3 171 Example 4 172 Wildcard Mask Keywords (4.2.4) 172 Guidelines for ACL Creation (4.3) 173 Limited Number of ACLs per Interface (4.3.1) 173 ACL Best Practices (4.3.2) 174 Types of IPv4 ACLs (4.4) 175 Standard and Extended ACLs (4.4.1) 175 Numbered and Named ACLs (4.4.2) 176 Numbered ACLs 176 Named ACLs 177 Where to Place ACLs (4.4.3) 177 Standard ACL Placement Example (4.4.4) 179 Extended ACL Placement Example (4.4.5) 180 Summary (4.5) 182 Purpose of ACLs 182 Wildcard Masks 182 Guidelines for ACL Creation 183 Types of IPv4 ACLs 183 Practice 184 Check Your Understanding Questions 184 Chapter 5 ACLs for IPv4 Configuration 187 Objectives 187 Key Term 187 Introduction (5.0) 188 Configure Standard IPv4 ACLs (5.1) 188 Create an ACL (5.1.1) 188 Numbered Standard IPv4 ACL Syntax (5.1.2) 188 Named Standard IPv4 ACL Syntax (5.1.3) 189 Apply a Standard IPv4 ACL (5.1.4) 190 Numbered Standard IPv4 ACL Example (5.1.5) 191 Named Standard IPv4 ACL Example (5.1.6) 193 Modify IPv4 ACLs (5.2) 195 Two Methods to Modify an ACL (5.2.1) 196 Text Editor Method (5.2.2) 196 Sequence Numbers Method (5.2.3) 197 Modify a Named ACL Example (5.2.4) 198 ACL Statistics (5.2.5) 199 Secure VTY Ports with a Standard IPv4 ACL (5.3) 200 The access-class Command (5.3.1) 200 Secure VTY Access Example (5.3.2) 200 Verify the VTY Port Is Secured (5.3.3) 202 Configure Extended IPv4 ACLs (5.4) 203 Extended ACLs (5.4.1) 203 Numbered Extended IPv4 ACL Syntax (5.4.2) 204 Protocols and Ports (5.4.3) 206 Protocol Options 206 Port Keyword Options 207 Protocols and Port Numbers Configuration Examples (5.4.4) 208 Apply a Numbered Extended IPv4 ACL (5.4.5) 209 TCP Established Extended ACL (5.4.6) 210 Named Extended IPv4 ACL Syntax (5.4.7) 212 Named Extended IPv4 ACL Example (5.4.8) 212 Edit Extended ACLs (5.4.9) 213 Another Named Extended IPv4 ACL Example (5.4.10) 214 Verify Extended ACLs (5.4.11) 216 show ip interface 216 show access-lists 217 show running-config 218 Summary (5.5) 219 Configure Standard IPv4 ACLs 219 Modify IPv4 ACLs 219 Secure VTY Ports with a Standard IPv4 ACL 220 Configure Extended IPv4 ACLs 220 Practice 221 Check Your Understanding Questions 222 Chapter 6 NAT for IPv4 225 Objectives 225 Key Terms 225 Introduction (6.0) 226 NAT Characteristics (6.1) 226 IPv4 Private Address Space (6.1.1) 226 What Is NAT? (6.1.2) 227 How NAT Works (6.1.3) 228 NAT Terminology (6.1.4) 229 Inside Local 230 Inside Global 230 Outside Global 231 Outside Local 231 Types of NAT (6.2) 231 Static NAT (6.2.1) 231 Dynamic NAT (6.2.2) 232 Port Address Translation (6.2.3) 233 Next Available Port (6.2.4) 235 NAT and PAT Comparison (6.2.5) 236 NAT 236 PAT 237 Packets Without a Layer 4 Segment (6.2.6) 237 NAT Advantages and Disadvantages (6.3) 238 Advantages of NAT (6.3.1) 238 Disadvantages of NAT (6.3.2) 238 Static NAT (6.4) 239 Static NAT Scenario (6.4.1) 240 Configure Static NAT (6.4.2) 240 Analyze Static NAT (6.4.3) 241 Verify Static NAT (6.4.4) 242 Dynamic NAT (6.5) 244 Dynamic NAT Scenario (6.5.1) 244 Configure Dynamic NAT (6.5.2) 245 Analyze Dynamic NAT-Inside to Outside (6.5.3) 247 Analyze Dynamic NAT-Outside to Inside (6.5.4) 248 Verify Dynamic NAT (6.5.5) 249 PAT (6.6) 251 PAT Scenario (6.6.1) 251 Configure PAT to Use a Single IPv4 Address (6.6.2) 252 Configure PAT to Use an Address Pool (6.6.3) 253 Analyze PAT-PC to Server (6.6.4) 254 Analyze PAT-Server to PC (6.6.5) 255 Verify PAT (6.6.6) 256 NAT64 (6.7) 258 NAT for IPv6? (6.7.1) 258 NAT64 (6.7.2) 258 Summary (6.8) 260 NAT Characteristics 260 Types of NAT 260 NAT Advantages and Disadvantages 261 Static NAT 261 Dynamic NAT 262 PAT 262 NAT64 263 Practice 264 Check Your Understanding Questions 264 Chapter 7 WAN Concepts 269 Objectives 269 Key Terms 269 Introduction (7.0) 272 Purpose of WANs (7.1) 272 LANs and WANs (7.1.1) 272 Private and Public WANs (7.1.2) 273 WAN Topologies (7.1.3) 274 Point-to-Point Topology 274 Hub-and-Spoke Topology 275 Dual-homed Topology 276 Fully Meshed Topology 276 Partially Meshed Topology 277 Carrier Connections (7.1.4) 278 Single-Carrier WAN Connection 278 Dual-Carrier WAN Connection 278 Evolving Networks (7.1.5) 279 Small Network 279 Campus Network 280 Branch Network 281 Distributed Network 282 WAN Operations (7.2) 283 WAN Standards (7.2.1) 283 WANs in the OSI Model (7.2.2) 284 Layer 1 Protocols 284 Layer 2 Protocols 284 Common WAN Terminology (7.2.3) 285 WAN Devices (7.2.4) 287 Serial Communication (7.2.5) 289 Circuit-Switched Communication (7.2.6) 290 Packet-Switched Communications (7.2.7) 290 SDH, SONET, and DWDM (7.2.8) 291 Traditional WAN Connectivity (7.3) 292 Traditional WAN Connectivity Options (7.3.1) 293 Common WAN Terminology (7.3.2) 293 Circuit-Switched Options (7.3.3) 295 Public Service Telephone Network (PSTN) 295 Integrated Services Digital Network (ISDN) 295 Packet-Switched Options (7.3.4) 295 Frame Relay 295 Asynchronous Transfer Mode (ATM) 296 Modern WAN Connectivity (7.4) 296 Modern WANs (7.4.1) 296 Modern WAN Connectivity Options (7.4.2) 297 Dedicated Broadband 297 Packet-Switched 298 Internet-Based Broadband 298 Ethernet WAN (7.4.3) 298 MPLS (7.4.4) 300 Internet-Based Connectivity (7.5) 301 Internet-Based Connectivity Options (7.5.1) 301 Wired Options 302 Wireless Options 302 DSL Technology (7.5.2) 302 DSL Connections (7.5.3) 303 DSL and PPP (7.5.4) 303 Host with PPPoE Client 304 Router PPPoE Client 304 Cable Technology (7.5.5) 305 Optical Fiber (7.5.6) 305 Wireless Internet-Based Broadband (7.5.7) 306 Municipal Wi-Fi 306 Cellular 306 Satellite Internet 307 WiMAX 307 VPN Technology (7.5.8) 308 ISP Connectivity Options (7.5.9) 309 Single-Homed 309 Dual-Homed 309 Multihomed 309 Dual-Multihomed 310 Broadband Solution Comparison (7.5.10) 311 Summary (7.6) 312 Purpose of WANs 312 WAN Operations 312 Traditional WAN Connectivity 313 Modern WAN Connectivity 314 Internet-Based Connectivity 314 Practice 315 Check Your Understanding Questions 316 Chapter 8 VPN and IPsec Concepts 319 Objectives 319 Key Terms 319 Introduction (8.0) 321 VPN Technology (8.1) 321 Virtual Private Networks (8.1.1) 321 VPN Benefits (8.1.2) 322 Site-to-Site and Remote-Access VPNs (8.1.3) 323 Site-to-Site VPN 323 Remote-Access VPN 324 Enterprise and Service Provider VPNs (8.1.4) 324 Types of VPNs (8.2) 325 Remote-Access VPNs (8.2.1) 325 SSL VPNs (8.2.2) 326 Site-to-Site IPsec VPNs (8.2.3) 327 GRE over IPsec (8.2.4) 328 Dynamic Multipoint VPNs (8.2.5) 330 IPsec Virtual Tunnel Interface (8.2.6) 331 Service Provider MPLS VPNs (8.2.7) 332 IPsec (8.3) 333 IPsec Technologies (8.3.2) 333 IPsec Protocol Encapsulation (8.3.3) 336 Confidentiality (8.3.4) 336 Integrity (8.3.5) 338 Authentication (8.3.6) 339 Secure Key Exchange with Diffie-Hellman (8.3.7) 342 Summary (8.4) 344 VPN Technology 344 Types of VPNs 344 IPsec 344 Practice 345 Check Your Understanding Questions 345 Chapter 9 QoS Concepts 351 Objectives 351 Key Terms 351 Introduction (9.0) 353 Network Transmission Quality (9.1) 353 Prioritizing Traffic (9.1.2) 353 Bandwidth, Congestion, Delay, and Jitter (9.1.3) 354 Packet Loss (9.1.4) 355 Traffic Characteristics (9.2) 357 Network Traffic Trends (9.2.2) 357 Voice (9.2.3) 358 Video (9.2.4) 358 Data (9.2.5) 360 Queuing Algorithms (9.3) 361 Queuing Overview (9.3.2) 361 First-In, First Out (9.3.3) 362 Weighted Fair Queuing (WFQ) (9.3.4) 362 Limitations of WFQ 363 Class-Based Weighted Fair Queuing (CBWFQ) (9.3.5) 364 Low Latency Queuing (LLQ) (9.3.6) 365 QoS Models (9.4) 366 Selecting an Appropriate QoS Policy Model (9.4.2) 366 Best Effort (9.4.3) 366 Integrated Services (9.4.4) 367 Differentiated Services (9.4.5) 369 QoS Implementation Techniques (9.5) 370 Avoiding Packet Loss (9.5.2) 371 QoS Tools (9.5.3) 371 Classification and Marking (9.5.4) 372 Marking at Layer 2 (9.5.5) 373 Marking at Layer 3 (9.5.6) 374 Type of Service and Traffic Class Field (9.5.7) 375 DSCP Values (9.5.8) 376 Class Selector Bits (9.5.9) 377 Trust Boundaries (9.5.10) 378 Congestion Avoidance (9.5.11) 379 Shaping and Policing (9.5.12) 380 QoS Policy Guidelines (9.5.13) 381 Summary (9.6) 382 Network Transmission Quality 382 Traffic Characteristics 382 Queuing Algorithms 383 QoS Models 383 QoS Implementation Techniques 384 Practice 385 Check Your Understanding Questions 385 Chapter 10 Network Management 389 Objectives 389 Key Terms 389 Introduction (10.0) 390 Device Discovery with CDP (10.1) 390 CDP Overview (10.1.1) 390 Configure and Verify CDP (10.1.2) 391 Discover Devices by Using CDP (10.1.3) 393 Device Discovery with LLDP (10.2) 396 LLDP Overview (10.2.1) 396 Configure and Verify LLDP (10.2.2) 397 Discover Devices by Using LLDP (10.2.3) 397 NTP (10.3) 400 Time and Calendar Services (10.3.1) 400 NTP Operation (10.3.2) 401 Stratum 0 402 Stratum 1 402 Stratum 2 and Lower 402 Configure and Verify NTP (10.3.3) 402 SNMP 405 Introduction to SNMP (10.4.1) 405 SNMP Operation (10.4.2) 406 SNMP Agent Traps (10.4.3) 408 SNMP Versions (10.4.4) 409 Community Strings (10.4.6) 412 MIB Object ID (10.4.7) 415 SNMP Polling Scenario (10.4.8) 415 SNMP Object Navigator (10.4.9) 417 Syslog (10.5) 418 Introduction to Syslog (10.5.1) 418 Syslog Operation (10.5.2) 420 Syslog Message Format (10.5.3) 421 Syslog Facilities (10.5.4) 422 Configure Syslog Timestamp (10.5.5) 422 Router and Switch File Maintenance (10.6) 423 Router File Systems (10.6.1) 424 The Flash File System 425 The NVRAM File System 425 Switch File Systems (10.6.2) 426 Use a Text File to Back Up a Configuration (10.6.3) 427 Use a Text File to Restore a Configuration (10.6.4) 428 Use TFTP to Back Up and Restore a Configuration (10.6.5) 428 USB Ports on a Cisco Router (10.6.6) 430 Use USB to Back Up and Restore a Configuration (10.6.7) 430 Restore Configurations with a USB Flash Drive 432 Password Recovery Procedures (10.6.8) 433 Password Recovery Example (10.6.9) 433 Step 1. Enter the ROMMON mode 433 Step 2. Change the configuration register 434 Step 3. Copy the startup-config to the running-config 434 Step 4. Change the password 435 Step 5. Save the running-config as the new startup-config 435 Step 6. Reload the device 435 IOS Image Management 437 TFTP Servers as a Backup Location (10.7.2) 437 Backup IOS Image to TFTP Server Example (10.7.3) 438 Step 1. Ping the TFTP server 438 Step 2. Verify image size in flash 439 Step 3. Copy the image to the TFTP server 439 Copy an IOS Image to a Device Example (10.7.4) 439 Step 1. Ping the TFTP server 440 Step 2. Verify the amount of free flash 440 Step 3. Copy the new IOS image to flash 441 The boot system Command (10.7.5) 441 Summary (10.8) 443 Device Discovery with CDP 443 Device Discovery with LLDP 443 NTP 443 SNMP 444 Syslog 444 Router and Switch File Maintenance 445 IOS Image Management 446 Practice 446 Check Your Understanding Questions 447 Chapter 11 Network Design 453 Objectives 453 Key Terms 453 Introduction (11.0) 455 Hierarchical Networks (11.1) 455 The Need to Scale the Network (11.1.2) 455 Borderless Switched Networks (11.1.3) 458 Hierarchy in the Borderless Switched Network (11.1.4) 459 Three-Tier Model 460 Two-Tier Model 461 Access, Distribution, and Core Layer Functions (11.1.5) 462 Access Layer 462 Distribution Layer 462 Core Layer 462 Three-Tier and Two-Tier Examples (11.1.6) 462 Three-Tier Example 463 Two-Tier Example 464 Role of Switched Networks (11.1.7) 464 Scalable Networks (11.2) 465 Design for Scalability (11.2.1) 465 Redundant Links 466 Multiple Links 466 Scalable Routing Protocol 467 Wireless Connectivity 468 Plan for Re

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