Chapter 13: Solving Network Problems

Chapter 13: Solving Network Problems

Learning Objectives Discuss the benefits of network management and planning Understand the necessity for networking standards, policies and procedures, and documentation Troubleshoot your network following a structured approach Discuss the types of specialized equipment and other resources available for troubleshooting Guide to Networking Essentials, Fourth Edition 2

Preventing Problems with Network Management and Planning Two ways to solve networking problems Prevent them through planning and management Called pre-emptive troubleshooting or trouble avoidance Repair and control damage that already exists Called troubleshooting Guide to Networking Essentials, Fourth Edition 3

Preventing Problems with Network Management and Planning (continued) Combine network management and troubleshooting to form overall network plan Include cable diagrams, cable layers, network capacity information, protocols and network standards, documentation on computer and network device configuration, software, and important files Establish network policies and procedures Include back-up methods, security, hardware and software standards, upgrade guidelines, and documentation Guide to Networking Essentials, Fourth Edition 4

Backing Up Network Data To prevent data loss, develop comprehensive back-up program, including: What data should be backed up and how often? What type of backup will be performed, how often, and what time? Who is responsible for performing backups? Is backup system being tested regularly? Is backup log complete? Where is backed-up data stored (on-site and off-site)? Table 13-1 shows several back-up methods Guide to Networking Essentials, Fourth Edition 5

Backup Methods Guide to Networking Essentials, Fourth Edition 6

Setting Security Policies Security policies are part of network plan Include both data and hardware security Primary data security is username and passwords for all accounts, including: How often users change passwords Whether users can reuse same passwords What character restrictions passwords have Whether passwords have single or multiple sets of standards How exceptions are defined and documented Guide to Networking Essentials, Fourth Edition 7

Setting Security Policies (continued) Establish guidelines for resource access Grant access only to users who require it Grant minimum levels of access Set special security requirements for dial-in accounts Keep to a minimum the number of users who perform network administration tasks Guide to Networking Essentials, Fourth Edition 8

Setting Hardware and Software Standards Set standards for all network components Determine supported hardware manufacturers and operating systems, including versions Determine what networking protocols and services will be used Define server configurations and guidelines for new server installations Evaluate standards at least once per quarter to keep network up to date Guide to Networking Essentials, Fourth Edition 9

Establishing Upgrade Guidelines Establish guidelines for upgrades Give users advance notice of changes Try not to perform upgrades during working hours First “pilot” upgrades with small group of astute network users to resolve problems Have plan to undo upgrade installation if necessary Guide to Networking Essentials, Fourth Edition 10

Maintaining Documentation Keep complete up-to-date documentation of network, both in hard copy and in electronic form, including: Address list Cable map Contact list Equipment list Network history Network map Guide to Networking Essentials, Fourth Edition Network hardware configuration Policies and procedures Server configuration Software configuration Software licensing User administration 11

Performing Pre-emptive Troubleshooting International Organization for Standardization (ISO) identifies five categories for pre-emptive network troubleshooting: Account management Configuration management Fault management Performance management Security management Guide to Networking Essentials, Fourth Edition 12

Practicing Good Customer-Relation Skills Users are customers, and the reason network personnel have jobs Best source of information when something goes wrong with network Develop special relationships with adept users Develop guidelines about user interaction Include how to question and respond to users, handle irate users, and general user communication etiquette Guide to Networking Essentials, Fourth Edition 13

Using Network-Monitoring Utilities Many programs help with network management Identify conditions that may lead to problems, prevent network failures, and troubleshoot problems Use network management utilities Learn which statistics to monitor Establish baseline for network performance Monitor changes Guide to Networking Essentials, Fourth Edition 14

Using Network-Monitoring Utilities (continued) Use network management utilities in advanced operating systems or from third-party sources Gather information about: Events System usage statistics System performance statistics Guide to Networking Essentials, Fourth Edition 15

Using Network-Monitoring Utilities (continued) Use information from utilities to help: Identify network devices that create bottlenecks Provide information to forecast growth and plan capacity requirements Develop plans to improve network performance Monitor events that arise from software or hardware changes Monitor trends in network traffic and utilization Figure 13-1 shows Windows XP Performance Monitor Guide to Networking Essentials, Fourth Edition 16

Windows XP Performance Monitor Guide to Networking Essentials, Fourth Edition 17

Creating a Network Baseline Defines point of reference for measuring network performance when problem occurs Create baseline over time when no problems are evident on network and repeat baseline periodically, especially after significant changes to network Compare network performance with baseline to help identify: Daily network utilization patterns Possible network bottlenecks Heavy usage patterns Protocol traffic patterns Guide to Networking Essentials, Fourth Edition 18

Monitoring with SNMP Simple Network Management Protocol (SNMP) is part of TCP/IP protocol suite Software agents for each network device monitor traffic and device status Store information in management information base (MIB) See Figure 13-2 Guide to Networking Essentials, Fourth Edition 19

SNMP Network Monitoring and Managing Guide to Networking Essentials, Fourth Edition 20

Monitoring with SNMP (continued) SNMP monitors agents and collects data in MIBs to generate statistics or charts about network Can set thresholds for SNMP managers Generate alerts when thresholds are exceeded Manage network components such as bridges and routers Can interrogate devices and make remote configuration changes Guide to Networking Essentials, Fourth Edition 21

Using Remote Monitoring (RMON) for Advanced Monitoring Two versions of RMON: RMON1 captures data and collects statistics at Data Link and Physical layers RMON2 collects and analyzes traffic at Network and higher layers Some devices are RMON-capable Contain software agents, called probes, that collect data and communicate with management station using SNMP Guide to Networking Essentials, Fourth Edition 22

Network Troubleshooting In spite of planning, monitoring, and other preemptive techniques, problems do occur Be ready to troubleshoot network to diagnose and fix problems, by using: Troubleshooting methodology Structured approach Special tools Guide to Networking Essentials, Fourth Edition 23

Troubleshooting Methodology Stay calm and use clear head to assess problems Steps to help troubleshoot common network problems include: Eliminate potential user errors Verify physical connections are working Verify status of any suspect NICs Restart computer Guide to Networking Essentials, Fourth Edition 24

Structured Approach Five-step structured troubleshooting approach for tackling complex network problems: Set problem’s priority Collect information about problem Develop list of possible causes Test each hypothesis to isolate actual cause For each potential cause, attempt at least one solution Guide to Networking Essentials, Fourth Edition 25

Prioritize Determine scope of problem Does it affect single computer or more If multiple problems, assign each a priority Tackle them in decreasing order of severity, starting with most severe problem Guide to Networking Essentials, Fourth Edition 26

Collect Information Ask user specific questions to obtain details Scan network for obvious problems or failures Review previous network problems to determine if problem is recurrent Determine scope of problem by dividing network into small parts and checking each Create troubleshooting checklist to make task more manageable Guide to Networking Essentials, Fourth Edition 27

Establish Possible Causes Create list of possible causes Rank them in order of likelihood Start with most likely cause Guide to Networking Essentials, Fourth Edition 28

Isolate the Problem Make only one change at a time and test it Be sure changes do not introduce new problem Document all hardware, software, or configuration changes Guide to Networking Essentials, Fourth Edition 29

Test Results After each change, test results to see if problem is fixed or new problem is introduced When problem is solved, document steps that implemented solution Include information in network documentation If change does not fix problem, move to next possible cause Sometimes a change reveals another deeper problem Guide to Networking Essentials, Fourth Edition 30

Using Special Tools Most problems occur at lower layers of OSI model where they are more difficult to troubleshoot Variety of special troubleshooting tools help diagnose problems, including: Digital voltmeter (DVM) Time-domain reflectometer (TDR) Basic and advanced cable testers Oscilloscopes Network monitors Protocol analyzers Guide to Networking Essentials, Fourth Edition 31

Digital Voltmeter (DVM) Also called volt-ohm meter (VOM) Basic electrical measuring device Can measure cable’s resistance to determine if it is broken Can detect short circuit in cable Guide to Networking Essentials, Fourth Edition 32

Time-Domain Reflectometer (TDR) Determines if cable has break or short By reflecting back from break, can pinpoint how far from device break occurs High quality TDR can come within few inches of break May be used with fiber-optic and electrical cables During new installation, use TDR to document actual lengths of cables Standard part of most advanced cable testers Guide to Networking Essentials, Fourth Edition 33

Basic Cable Testers Test correct termination of twisted-pair cable Test continuity of coaxial cable Excellent for checking patch cables Do not detect breaks in cables Do not check for attenuation, noise, or other performance problems Guide to Networking Essentials, Fourth Edition 34

Advanced Cable Testers Combine characteristics of DVM, TDR, and protocol analyzer Detect where break is located in cable Gather information about cable’s impedance, resistance, and attenuation Function at Physical and Data Link layers of OSI model Can measure frame counts, collisions, congestion, beaconing information, or broadcast storms Guide to Networking Essentials, Fourth Edition 35

Oscilloscopes Measure signal voltage over time Identify shorts, sharp bends or crimps, cable breaks, and attenuation problems Guide to Networking Essentials, Fourth Edition 36

Network Monitors Software that tracks network traffic, including packet types, errors, traffic to and from each computer Can generate reports and graphs Included with Windows NT, 2000/2003 Server versions and also available from third parties Guide to Networking Essentials, Fourth Edition 37

Protocol Analyzers Most advanced network troubleshooting device Evaluates overall health of network Monitors all traffic in real time Captures traffic and decodes packets Looks inside packets to determine problems Generates network statistics Can establish baseline for network and troubleshoot problems Most advanced ones combine hardware and software Especially good for Layer 3 (Network) devices Some protocol analysis capability in Window’s Network Monitor Guide to Networking Essentials, Fourth Edition 38

Network Support Resources Variety of network support resource formats Software products Online services Subscription services Printed material Guide to Networking Essentials, Fourth Edition 39

Microsoft TechNet Microsoft Technical Information Network (TechNet) is subscription service Includes monthly set of CD-ROMs with product information, technical support updates, software drivers, and online tutorials Valuable tool for gathering information and diagnosing network problems Easy-to-use interface Online version is free Guide to Networking Essentials, Fourth Edition 40

Microsoft Knowledge Base Provides information from interaction with customers by technical support staff Available free on Web or by subscription Guide to Networking Essentials, Fourth Edition 41

Linux Information Resource Many Linux resources, including: www.linux.com - search engine for information, downloads, pointers, and documentation Everything Linux at www.eunuchs.org - tips, tricks, and troubleshooting techniques www.linux.org – provides the latest news, kernel releases, and links to Linux distributions among other goodies Guide to Networking Essentials, Fourth Edition 42

Novell NetWare Information Sources http://support.novell.com - searchable knowledge base Provides articles and notices about known problems, bug fixes, workarounds, and patches Contains driver updates and operating system service patches Guide to Networking Essentials, Fourth Edition 43

Online Support Services and Newsgroups Many online support services, including: Microsoft Developer’s Network (MSDN) at http://msdn.microsoft.com Other Microsoft newsgroups at msnews.microsoft.com www.sunbelt-software.com - Windows mailing list Guide to Networking Essentials, Fourth Edition 44

Periodicals Many deal specifically with computers and networking and are available over Internet or offer free subscriptions Most popular journals include: LAN Magazine LAN Times Communications Week International InfoWorld Guide to Networking Essentials, Fourth Edition eWeek PC Magazine (Network Edition) Network Computing Windows & .Net Magazine Linux Journal 45

Common Troubleshooting Situations Some of most common network problems involve: Cabling and related components Power fluctuations Upgrades Poor network performance Guide to Networking Essentials, Fourth Edition 46

Cabling and Related Components Majority of network problems occur at Physical layer and involve cables, connectors, and NICs Make sure cable is properly connected and correct kind Be sure length is within maximum limit for type of medium Check LEDs on NIC, if available Exchange NIC with known working one Use PING utility to check connectivity to other computers Guide to Networking Essentials, Fourth Edition 47

Power Fluctuations Caused by electrical storm or power failure Adversely affect computers Afterwards, verify that servers are up and functioning Use Uninterruptible Power Supplies (UPSs) Especially important for servers Provide battery power so computers can be brought down without data loss Some perform automatic shutdowns Guide to Networking Essentials, Fourth Edition 48

Upgrades Constantly changing technology makes it necessary to upgrade equipment and software frequently Some important considerations when performing network upgrades: Keep current and do one upgrade at a time Ignoring upgrades may require complete network overhaul Test any upgrade before deploying it Inform users about upgrade: when it will occur, what is involved, and what to expect Guide to Networking Essentials, Fourth Edition 49

Poor Network Performance If network slows over time, ask these questions to pinpoint causes: What has changed? Have new equipment or applications been added? Is someone playing electronic games across network? Are there new users on network? How many? Is other new equipment, such as a generator, causing interference near network? May be necessary to expand network to increase current capacity Guide to Networking Essentials, Fourth Edition 50

Chapter Summary Network management, planning, and monitoring are critical parts of network administrator’s job Proper management can avoid or minimize potential problems Avoiding problems is better than solving problems Key to pre-emptive troubleshooting is to understand and apply OSI network-management model, consisting of accounting, configuration, performance and security management Guide to Networking Essentials, Fourth Edition 51

Chapter Summary (continued) Planning is key part of network management Planning includes setting back-up schedules and guidelines, security guidelines, hardware and software standards, and upgrade guidelines Create written plans, policies, and procedures Maintain a complete set of network documentation Guide to Networking Essentials, Fourth Edition 52

Chapter Summary (continued) Many programs are available to assist with network management and monitoring Using tools to monitor your network, you can establish a network performance baseline against which to identify anomalies When an error occurs, use structured, methodical approach to troubleshooting eases tension and ensures that all possible solutions are covered Many tools and resources help troubleshoot network Guide to Networking Essentials, Fourth Edition 53

Chapter Summary (continued) For difficult problems, fall back on structured network troubleshooting approach Change is most common cause of network problems Try to identify what has changed since change is most common cause of network problems Common sources of problem-causing changes include adding new equipment or software, upgrading existing software or equipment, and workload or workplace behavior that results in increased traffic or network utilization Guide to Networking Essentials, Fourth Edition 54