IP路由技术基础 英文版PDF电子书下载

Chapter 1 Topology and Router Configurations 1

Understanding the Role of Routers in Networks 1

The Router Interface 2

Network Layer Addresses 2

Datagrams 3

MAC Addresses 4

IP Address Formats 5

Network Reference Models 6

Understanding Topology and Router Configurations 9

RouterA s Configuration 10

RouterB s Configuration 11

RouterC s Configuration 12

Understanding What a Router Does 13

Sample Network 13

How a Router Knows What to Do 15

Choosing Your Routing Protocol 16

Understanding How Forwarding Decisions Are Made 18

Performing Longest Match Lookups 18

Forwarding Decisions for Multipoint Interfaces 21

End Systems Sending Packets to Other Subnets 23

Summary 25

Chapter2 Routing Metrics and Distances 27

Primary Activities of Convergence 27

Viewing the Invalid Timers in a Routing Table 29

Viewing an Expired Invalid Timer in a Routing Table 30

Router Still Uses a Path 33

Understanding Convergence 37

Parallel Paths 38

The Effect of Parallel Paths on Convergence 38

Looking at Parallel Paths in a Routing Table 39

Convergence in Action 40

The Routing Table After Convergence 41

Step-by-Step Review of Convergence 43

Debug Messages and Reality 46

When Holddown Is Initiated 46

Understanding Parallel Paths and Their Effect on Packet Forwarding 47

Process Switching Versus Fast Switching 50

Configuring Process Switching 51

Configuring Fast Switching 52

Understanding the Role of Split Horizon 54

Routing Advertisements with Split Horizon Enabled 56

Routing Advertisements with Split Horizon Disabled 57

Routing Loops Caused by Disabling Split Horizon 60

Loss of a Connected Route Versus a Dynamic Route 64

Split Horizon s Effect on Multipoint WAN Interfaces 65

Using Subinterfaces to Avoid Problems Caused by Split Horizon 68

Poison Reverse and Triggered Updates 70

IGRP Routing Metrics (Variables) and Cisco Administrative Distances 72

IGRP Metrics (Variables) 73

Administrative Distances 74

Running Multiple Routing Protocols Concurrently 76

Altering IGRP S Bandwidth and Delay Variables 79

Problems with Manipulating the Delay Variable 83

Understanding the Effects of Manipulating the Delay Variable 84

Understanding the Effects of Manipulating the Bandwidth Variable 87

Calculating IGRP Metrics 90

Summary 93

Chapter3 Discontiguous Networks, Summarization, and Subnet 0 95

Introduction to Terminology 96

Discontiguous Networks Using RIP and IGRP 98

Understanding How a Router Derives thd Correct Masks 99

Understanding Summarization (Summarized Routes) 103

Understanding Subnet 0 104

Summarized Routes Versus Subnet 0 105

Summarization Caused by Discontiguous Networks in Action 106

RIP Cannot Reach Discontiguous Subnets 107

Discontiguous Networks, Subnet 0, and Summarization Using IGRP 109

Discontiguous Networks Using Two Routers 111

Discontiguous Networks Using Three Routers 112

When Connectivity Is Possible 112

When Connectivity Is Not Possible 120

Alternating Paths for the First Ping 124

Using Other Routing Protocols 126

Using Summarization as a Tool 127

Summary 129

Chapter4 Using IP Unnumbered and VLSM 131

Understanding IP Unnumbered 133

IP Unnumbered Causes Host Routes and Lost Connectivity 133

Host Routes 134

Hosts Routes Using DDR 135

Configuring IP Unnumbered on Serial Interfaces 138

RIP and IGRP Behave the Same 139

RIP with IP Unnumbered Configured Properly 140

Displaying the Routes 140

Sending Routing Updates 141

RIP with IP Unnumbered Configured Improperly 142

Pinging the Interfaces 142

Examples of Routing Updates 144

Host Route Problem 145

Lost Routes Problem 146

Using a Different Subnet Mask and a Different Major Net 147

Understanding VLSM 153

VLSM Using RIP and IGRP 153

VLSM Experiment Using Two Routers 154

VLSM Experiment Using Three Routers 157

Correctly Configuring VLSM Blocked Routes 160

VLSM Summary 162

Summary 162

Introduction to Default Routing 163

Chapter5 Default Routing 163

Gateway of Last Resort 165

Gateway of Last Resort for a Non-Local Domain 168

Gateway of Last ResortFails for a Local Domain 169

Gateway of Last Resort Still Works When Links Fail 173

Using IP Classless 174

In Review 175

Using Default and Static Routes in Complicated Networks 177

Using Static Routes 177

Dealing with Too Much Default Routing Information 179

Fixing a Default Gateway Loop 185

RIP and 0.0.0.0 187

The 0.0.0.0 Default Route 187

Using 0.0.0.0 with IGRP 198

What to Do Instead of Using 0.0.0.0 with IGRP 198

Using End Systems with Multiple Local Gateways 203

ICMP Router Discovery Protocol (IRDP) RFC 1256 204

End Systems Using RIP 205

Cisco s Hot Standby Router Protocol (HSRP) 209

Using Floating Static Routes 212

Summary 215

Chapter 6 IP Troubleshooting Scenarios 217

Developing a Troubleshooting Routine 217

Using a Troubleshooting Scenario 219

Tracing the Route 220

Checking the Available Routes 220

Using Extended Pings to Track Connectivity 223

Other Possible Problems 225

An ARP Problem 225

Validating End System Routing Tables 226

Summary 230

Chapter7 Bridging IP Between Dissimilar Media 233

Translational Bridging 233

MSB Versus LSB 234

Bit Swapping MAC Addresses 235

ARP Explained 237

Translating Bridges and ARP Frames 239

ARP in Action 240

Vendor-Specific Solutions to ARP 243

Static ARPs 245

Displaying the Parameters of the ARP.EXE Command 245

Displaying the Current ARP Entries 246

How to Create a Static ARP Entry and Display It 246

Deleting Static ARP Entries 246

Summary 247

Chapter8 Hexadecimal and Binary Numbering and IP Addressing 249

Binary Numbering Versus Decimal Numbering 249

Hexadecimal Numbering Versus Decimal Numbering 252

Introduction to the 32-B it IP Address 255

Classes of Addresses 256

Default Subnet Masks for Class A, B, C, and D Addresses 257

Understanding Subnet Masks, Subnetting, and Supernetting 258

Determining What Subnet Is Being Used 263

The Shorthand Subnet Mask Indicator 265

Introduction to Supernetting 266

Calculating Subnet and Host Combinations 267

Summary 267

Appendix A RFCs 269

How RFCs Work 269

RFCs Recommended for Further Study 270

RFC2235: Hobbes Internet Timeline 270

RFC2031: IETF-ISOC Relationship 271

RFC2028: The Organizations Involved in the IETF Standards Process 271

RFC2200: Internet Official Protocol Standards 271

RFC2101: IPv4 Address Behavior Today 271

RFC2151: A Primer on Internet and TCP/IP Tools and Utilities 271

RFC2027: IAB and IESG Selection, Confirmation, and Recall Process: Operation of the Nominating and R 272

RFC2026: The Internet Standards Process: Revision3 272

RFC2008: Implications of Various Address Allocation Policies for Internet Routing 272

RFC1935: What Is the Internet, Anyway? 272

RFC1925: The Twelve Networking Truths 272

RFC1812: Requirements for IP Version 4 Routers 273

RFC1917: An Appeal to the Internet Community to Return Unused IP Networks (Prefixes) to the IANA 273

RFC1878: Variable Length Subnet Table for IPv4 273

RFC1923: RIPv1 Applicability Statement for Historic Status 273

RFC1918: Address Allocation for Private Internets 273

RFC1631: The IP Network Address Translator (NAT) 274

RFC1601: Charter of the Internet Architecture Board (IAB) 274

RFC1508: Guide to Network Resource Tools 274

RFC1393: Traceroute Using an IP Option 274

RFC1256: ICMP Router Discovery Messages 274

RFC1058: Routing Information Protocol 275

RFC826: An Ethernet Address Resolution Protocol 275

RFC1700: Assigned Numbers 275

RFC1149: A Standard for the Transmission of IP Datagrams on Avian Carriers 275

RFC1178: Choosing a Name for Your Computer 275

RFC1180: A TCP/IP Tutorial 275

RFC1543: BOOTP 276

RFC2283, RFC1966, RFC1965, RFC1774, RFC1773, RFC1772, RFC1771, RFC1745: Border Gateway Protocol V4 ( 276

RFC1817, RFC1520, RFC1519, RFC1518, RFC1517: Classless Interdomain Routing (CIDR) 276

RFC2132, RFC2131, RFC1534: Dynamic Host Configuration Protocol (DHCP) 277

RFC2308, RFC2230, RFC2219, RFC2182, RFC2181, RFC2136, RFC2052, RFC1996, RFC1995, RFC1912, RFC1794, R 277

RFC2178, RFC1745, RFC1587, RFC1586, RFC1585, RFC1584, Open Shortest Path First (OSPF) 278

RFC1931, RFC1293: Reverse Address Resolution Protocol (RARP) Inverse RARP 278

RFC2092, RFC2091, RFC1723, RFC1722, RFC1721, RFC1582, RFC1581: RIP 278

RFC2072, RFC2071: Router Renumbering 279

RFC2001: TCP/IP (TCP) Slow Start 279

RFC1470: TCP/IP Debugging Tools 279

Summary 280

Index 281