CONTENTS Title Page Copyright Page Preface 1 Overview of Data Communications Networks 1.1 What Is a Data Communications Network? 1.1.1 What Are the Components? 1.1.2 What Does a Data Communications Network Look Like? 1.1.2.1 Star Topology 1.1.2.2 Ring Topology 1.1.2.3 Bus Topology 1.1.2.4 Mesh Topology 1.1.2.5 Tree Topology 1.1.2.6 Local Area Network Topology 1.1.2.7 Wide Area Network Topology 1.2 What Is a DECnet Network? 1.2.1 What Does a DECnet Network Look Like? 1.2.2 What Communications Media Does DECnet Use? 1.2.2.1 What is Ethernet/802.3? 1.2.3 How Do Systems Communicate over DECnet? 1.2.4 How Does DECnet Route Messages? 1.2.5 How Is DECnet Software Structured? 1.2.6 What Systems Can Communicate over the Network? 1.2.7 What Network Environments Does DECnet Support? 1.2.7.1 Local Area Networks 1.2.7.2 Wide Area Networks 1.3 What Is an Internet Network? 1.3.1 What Does an Internet Look Like? 1.3.2 What Is TCP/IP and How Is It Structured? 1.3.3 What Are Addressing, Naming, and Routing? 1.3.4 Addressing 1.3.4.1 Common Internet Address Notation 1.3.4.2 Network Classes 1.3.4.3 Subnet Addressing 1.3.4.3.1 Advantages of Subnet Addressing 1.3.4.3.2 Subnets and Internet Addresses 1.3.4.3.3 Address Masks 1.3.5 Naming 1.3.5.1 Domain Name System 1.3.5.2 Name Servers 1.3.6 Routing 1.3.6.1 IP Routing Tables 1.3.6.2 Direct Routing 1.3.6.3 Indirect Routing 1.3.6.4 Routing In the Presence of Subnets 1.3.7 Network Protocols 1.3.7.1 Internet Protocol 1.3.7.2 Routing Protocols 1.3.7.3 Routing Information Protocol 1.3.7.4 Internet Control Message Protocol (ICMP) 1.3.8 Transport Protocols 1.3.8.1 Transmission Control Protocol 1.3.8.2 User Datagram Protocol 1.3.9 Other Protocols 1.3.9.1 Address Resolution Protocol 1.3.9.2 Simple Network Management Protocol 2 Network Troubleshooting Methodology 2.1 Knowing Your Network 2.1.1 Topology 2.1.2 Architecture 2.1.2.1 Using DECnet Architectural Information in Problem Solving 2.1.2.2 Using TCP/IP Architectural Information in Problem Solving 2.1.3 Performance 2.1.4 Typical Use 2.2 Overview of the Network Troubleshooting Methodology 2.2.1 Applying The Methodology to Network Problems 2.3 Detecting a Problem 2.4 Obtaining and Refining the Problem Statement 2.5 Gathering Information 2.6 Analyzing, Interpreting, and Classifying Information 2.6.1 Extent of the Problem 2.6.1.1 Node or Host Problems 2.6.1.2 LAN Problems 2.6.1.3 WAN Problems 2.6.2 Types of Errors 2.6.2.1 Hard Errors 2.6.2.2 Inconsistent Errors 2.6.2.3 Intermittent Errors 2.6.2.4 Transient Errors 2.6.3 Sources of Errors 2.6.3.1 User Errors 2.6.3.2 Hardware Errors 2.6.3.3 Software Errors 2.6.3.4 Configuration Errors 2.6.3.5 Interoperability Errors 2.7 Isolating the Source of the Problem 2.7.1 Isolating to the Node or Host Level 2.7.2 Isolating to the LAN Level 2.7.3 Isolating to the WAN Level 2.8 Solving the Problem 2.9 Verifying the Solution 2.10 Cleaning Up 2.11 Verifying the Solution Again 2.12 Documenting the Problem and Solution 3 Network Management and Troubleshooting Tools arp command Authorize Utility Breakout Boxes DEC Extended LAN Management Software DECmcc Management Station for ULTRIX LAN Traffic Monitor LAT Control Program netstat command Network Control Program NMCC/DECnet Monitor NMCC/VAX ETHERnim ping command Protocol Analyzers syslog daemon Terminal Server Manager Software traceroute command uerf command 4 Resources for Troubleshooting 4.1 Log Files 4.1.1 VMS OPCOM and the Operator Log File 4.1.2 VMS Netserver Log File 4.1.3 VMS Error Log File 4.1.4 VMS Accounting Log File 4.1.5 ULTRIX Error Log Files 4.2 Routing Path Trace Procedures 4.2.1 NCP Routing Path Trace Procedure 4.2.2 netstat Routing Path Trace Procedure 4.3 NCP Loopback Tests 4.3.1 NCP Loopback Test Results 4.3.2 Types of Loopback Tests 4.3.3 Node-Level Tests 4.3.3.1 Remote Loopback Test 4.3.3.2 Local and Remote Loopback Tests Using a Loop Node Name 4.3.3.2.1 Local-to-Remote Testing 4.3.3.3 Local Loopback Test 4.3.4 Circuit-Level Tests 4.3.4.1 Software Loopback Test 4.3.4.2 Controller Loopback Test 4.3.4.3 Modem Loopback Tests 4.3.4.4 Using Loopback Tests to Check Circuitry 4.4 Reachability Tests for TCP/IP Networks 4.5 NCP Counters 4.5.1 Errors Applicable to Node Problems 4.5.2 Errors Applicable to LAN Problems 4.5.3 Errors Applicable to WAN Problems 4.5.4 Errors Applicable to Node, LAN, and WAN Problems 4.5.5 Formulas for Understanding Counters 4.5.5.1 Packet Rate 4.5.5.2 Circuit Quality 4.5.5.3 Transit Congestion Loss 4.5.5.4 Ethernet Line Statistics 4.5.5.5 Retransmissions 4.5.5.6 Routing Overhead 4.6 ULTRIX Counters 4.7 DECnet Events 5 Network Troubleshooting Procedures 5.1 Organization 5.2 Troubleshooting Notes Aborted Service Request Adjacency Rejected/Adjacency Up Asynchronous DECnet Problems Babbling Device Broadcast Storm Circuit State Problems Connect Failed, Access Control Rejected Connect Failed, Unrecognized Object Connection Timed Out Device Not Mounted Dialup Problems Host Is Unreachable Insufficient Resources at Remote Node Invalid Parameter Value LAN Bridge Cannot Downline Load LAN Segment Communication Problem LAT Port Hung LAT Print Queue Problems Line Synchronization Lost Login Incorrect Login Information Invalid Network Is Unreachable Network Object Unknown Network Partner Exited Node Out of Range Packet Loss Partial Routing Update Loss Partitioned Area Permission Denied Remote Node Is Not Currently Reachable Terminal Server Connection Failures Unknown Host Verification Reject A Ethernet Configuration Guidelines A.1 Baseband Ethernet A.2 ThinWire Ethernet A.3 Fiber-Optic Cable A.4 DELNI Local Network Interconnect A.5 DEMPR ThinWire Multiport Repeaters A.6 DEREP Ethernet Repeaters A.7 Bridges B RFC Request Process B.1 Obtaining RFCs Through The Internet File Transfer Protocol B.1.1 Logging In To The Remote Host B.1.2 Using Public Directories on The Remote Host B.1.3 Obtaining an Index of Available RFCs B.1.4 Copying RFC Files B.1.5 Logging Out of The Remote Host B.2 Obtaining RFCs Through The NIC Automatic Mail Service B.3 Obtaining RFCs by Telephone Request Glossary EXAMPLES 3-1 Authorize Utility Example 3-2 LAN Traffic Monitor Example 3-3 VMS LATCP Example 3-4 ULTRIX lcp Example 3-5 netstat -i Example 3-6 VMS Network Control Program Example 3-7 ULTRIX Network Control Program Example 3-8 Long Output from the ping Command 3-9 syslog Example 3-10 Terminal Server Manager Example 3-11 uerf Example 4-1 netstat Routing Path Trace 5-1 SYSGEN SHOW/DEVICE Display FIGURES 1-1 Point-to-Point Connections 1-2 Ethernet Connections 1-3 Star Topology 1-4 Ring Topology 1-5 Bus Topology 1-6 Mesh Topology 1-7 Tree Topology 1-8 Network Nodes, Circuits, and Lines 1-9 DECnet Network Architecture (DNA) Layers and Protocols 1-10 Small Local Area Network Configuration 1-11 Large Local Area Network Configuration 1-12 DDCMP Connections 1-13 Wide Area Network Connections 1-14 Large Integrated DECnet Configuration 1-15 Two Networks Interconnected to Form an Internet 1-16 Multiple Networks Interconnected to Form an Internet 1-17 Internet Protocol Model 1-18 Parts of an Internet Address 1-19 Internet Address Fields 1-20 Common Internet Address Notation 1-21 Internet Address Format for Network Classes 1-22 Internet Network Hierarchies 1-23 Internet Without Subnets 1-24 Internet with Subnets 1-25 Internet Subnet Address Parts 1-26 Internet Name Domains 1-27 Name Server Process 1-28 Internet Routing Process 1-29 Subnet Routing Examples 2-1 Network Troubleshooting Methodology 2-2 Unreachable DECnet Node or TCP/IP Host 2-3 Isolating the Source of the Problem 4-1 NCP Routing Path Trace Procedure 4-2 Components and Points of Loopback Testing 4-3 Remote Loopback Test 4-4 Local-to-Remote Loopback Test Using a Loop Node Name 4-5 Local-to-Local Loopback Test Using a Loop Node Name 4-6 Local Loopback Test 4-7 Software Loopback Test 4-8 Controller Loopback Test 4-9 Modem Loopback Tests 5-1 ULTRIX Access Control 5-2 VMS Access Control 5-3 Area Partitioned Due to Multiple Failures 5-4 Area Partitioned Due to Configuration Weaknesses TABLES 1-1 DECnet Layers 1-2 TCP/IP Layers 1-3 Sizes of Internet Network Classes 1-4 Address Ranges for Network Classes 1-5 Internet Address Fields Available For Subnets 1-6 Internet Domains 2-1 Tools for Node or Host Problems 2-2 Tools for LAN Problems 2-3 Tools for WAN Problems 3-1 Network Management and Troubleshooting Tools 3-2 ULTRIX netstat Command Options 3-3 Options for the ping Command 3-4 ULTRIX traceroute Command Options 3-5 ULTRIX uerf Command Options 5-1 Network Problems and Extent of Disturbance on the Network 5-2 NCP Executor Proxy Access Parameters 5-3 LAN Bridge 100 or 150 Indicator Lights 5-4 LAN Bridge 100 or 150 Switch Settings 5-5 Print Queue States and Conditions 5-6 NCP Proxy Access Parameters B-1 Public Directories on NIC.DDN.MIL