Network Troubleshooting

Overview A network administrator’s job has many aspects, all of which must be mastered through experience and education. Troubleshooting network problems is no exception. Some administrators can easily hone in on a problem; others take a while to get the hang of it. There simply is no magic wand for troubleshooting—each administrator needs to become very familiar with their network and how it should act.

Topics Troubleshooting Models TCP/IP Troubleshooting Utilities Hardware Troubleshooting Tools System Monitoring Tools Network Baselining

First Things First Check the obvious Check the trouble indicators Correct syntax User error Correct components Correct configuration Check the trouble indicators Warning lights Error messages and log files Is the problem hardware or software? Is the problem a single or multiple workstation? Check the cables June 20, 2011

Troubleshooting Recognition Diagnosis Resolution

Troubleshooting Models Step-by-step approach Administrator

The CompTIA Network+ Troubleshooting Model 1. Establishing the symptoms and potential causes 2. Identifying the affected area 3. Establishing what has changed 4. Selecting the most probable cause 5. Implementing an action plan and solution 6. Testing the result 7. Identifying the results and effects of the solution 8. Documenting the solution and process

The Network+ Troubleshooting Model – Step 1 1. Establishing the symptoms and potential causes Gather information Re-create the problem List potential causes 2. Identifying the affected area 3. Establishing what has changed 4. Selecting the most probable cause 5. Implementing an action plan and solution 6. Testing the result 7. Identifying the results and effects of the solution 8. Documenting the solution and process

The Network+ Troubleshooting Model – Step 2 1. Establishing the symptoms and potential causes 2. Identifying the affected area One user Several users One server One segment The network 3. Establishing what has changed 4. Selecting the most probable cause 5. Implementing an action plan and solution 6. Testing the result 7. Identifying the results and effects of the solution 8. Documenting the solution and process

The Network+ Troubleshooting Model – Step 3 1. Establishing the symptoms and potential causes 2. Identifying the affected area 3. Establishing what has changed Could you ever do this? When did things change? What has changed? 4. Selecting the most probable cause 5. Implementing an action plan and solution 6. Testing the result 7. Identifying the results and effects of the solution 8. Documenting the solution and process

The Network+ Troubleshooting Model – Step 4 1. Establishing the symptoms and potential causes 2. Identifying the affected area 3. Establishing what has changed 4. Selecting the most probable cause Start with most obvious cause Work backward Try simple solutions 5. Implementing an action plan and solution 6. Testing the result 7. Identifying the results and effects of the solution 8. Documenting the solution and process

The Network+ Troubleshooting Model – Step 5 1. Establishing the symptoms and potential causes 2. Identifying the affected area 3. Establishing what has changed 4. Selecting the most probable cause 5. Implementing an action plan and solution Create a plan Determine potential effects of the plan Implement step by step 6. Testing the result 7. Identifying the results and effects of the solution 8. Documenting the solution and process

The Network+ Troubleshooting Model – Step 6 1. Establishing the symptoms and potential causes 2. Identifying the affected area 3. Establishing what has changed 4. Selecting the most probable cause 5. Implementing an action plan and solution 6. Testing the result Verify that it solved the problem Verify that no new problems introduced Test various conditions 7. Identifying the results and effects of the solution 8. Documenting the solution and process

The Network+ Troubleshooting Model – Step 7 1. Establishing the symptoms and potential causes 2. Identifying the affected area 3. Establishing what has changed 4. Selecting the most probable cause 5. Implementing an action plan and solution 6. Testing the result 7. Identifying the results and effects of the solution Re-examine your list of potential effects Test for potential effects Adjust if needed 8. Documenting the solution and process

The Network+ Troubleshooting Model – Step 8 1. Establishing the symptoms and potential causes 2. Identifying the affected area 3. Establishing what has changed 4. Selecting the most probable cause 5. Implementing an action plan and solution 6. Testing the result 7. Identifying the results and effects of the solution 8. Documenting the solution and process Use a troubleshooting template Document all information Maintain records for reference

Troubleshooting IP Configuration Incorrect IP configuration

Troubleshooting with Ping Ping to local system succeeds Ping to default gateway fails

Troubleshooting with Tracert Start troubleshooting at last valid connection

Troubleshooting with Arp Incorrect mapping

Troubleshooting with Telnet 1 Upper-level service fails 2 Use Telnet to connect C:\> telnet 10.1.1.3 Password:

Troubleshooting with Nbtstat Server service running as desired

Troubleshooting with Netstat Queue shows activity No adapter errors Connection valid Listening ports valid

Troubleshooting with FTP Patches and utilities Vendor FTP site FTP client

Troubleshooting with Nslookup Verify default server Verify that server is responding to queries Verify that server can resolve names

Network Technician’s Hand Tools Various small hand tools

Electrical Safety Rules Professionals should service high-power equipment Always disconnect before servicing Work with a partner Never bypass safety devices Use anti-static devices

Wire Crimpers Specific to media type

Strips insulation and embeds wire A Punch Down Tool OV #: 16-24 Source File Name(s): Will need photo – here’s a sample from google Figure File Name: F08582116-14.png Comments: Nancy to add callouts when photos are taken. Strips insulation and embeds wire

Displays circuit status A Circuit Tester Plugs into socket Displays circuit status OV #: 16-25 Source File Name(s): Will need photo – sample from Google here Figure File Name: F08582116-15.png Comments: Nancy to add callouts when photos are taken.

Voltmeters Digital Analog

Ports for network cable Adapters for different network types A Cable Tester Ports for network cable Displays media status OV #: 16-27 Source File Name(s): Will need photo – here’s a sample from google Figure File Name: F08582116-17.png Comments: Nancy add callouts with photo Adapters for different network types

Wires crossed over internally Crossover Cables OV #: 16-28 Source File Name(s): THIS PHOTO needs replacing – need to show both ends of cable. Figure File Name: F08582116-18.png Comments: Nancy add callouts with photo Wires crossed over internally

A Hardware Loopback Plug OV #: 16-29 Source File Name(s): Will need photo – here’s a sample from google Figure File Name: F08582116-19.png Comments: Nancy add callouts with photo Crosses over transmit/receive lines

LED Indicator Lights Link light Activity light OV #: 16-30 Source File Name(s): Will need photo – can shoot back of any PC, use Nancy’s laptop if needed Figure File Name: F08582116-20.png Comments: Add callouts with photo

Tone Generators and Tone Locators Probe detects signal Port for network cable OV #: 16-31 Source File Name(s): Will need photo – here’s a sample from google Figure File Name: F08582116-21.png Comments: add callouts with photo Tone generator Tone locator

Network Analyzers Network Analyzers Protocol analyzers Windows 2000 = Network monitor Novell = LANalyzer Other third party Protocol analyzers Evaluate the data at all layers of the OSI model Operate in promiscuous mode

A Performance Monitor Displays results Nov. 8, 2014 Monitors counters

Displays frame contents A Protocol Analyzer Captures frames Displays frame contents

The Protocol Analysis Process Capture frames Decode contents Analyze contents

Using the Baseline Predict the impact of changes to network Use to find the reason for degradation in performance Show best locations to invest money in the network

Record of normal performance A Baseline Record of normal performance Various tests Baseline Record of current performance Basis for identifying abnormal conditions Starting point for improving performance

8. Upgrade or reconfigure The Baseline Process 1. Evaluate network 8. Upgrade or reconfigure as needed 2. Design tests 7. Repeat tests when performance low 3. Schedule tests 4. Run tests 6. Analyze data 5. Document results

Renewing the Baseline When do you redo your baseline? When role of network changes When services are added to network When services are removed from network

Reflective Questions Describe a troubleshooting situation you were involved in, or that you read or heard about. Was it resolved through a structured methodology? Which of the troubleshooting tools and processes presented in this lesson do you think you will find most useful or use most frequently? Why?

Collect, Isolate, and Correct Model Collect information Isolate the problem Correct the problem

Tools help you troubleshoot only if you have mastered their use Network Support Tools Tools help you troubleshoot only if you have mastered their use Software-based tools Diagnostic utilities Performance monitors TCP/IP Utilities