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Fundamentals of Networking

Fundamentals of Networking. Discovery 1, Chapter 9 Troubleshooting. Objectives. Describe the troubleshooting process Describe the utilities used to verify TCP/IP connectivity Identify & describe common hardware and connection issues in wired and wireless networks

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Fundamentals of Networking

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  1. Fundamentals of Networking Discovery 1, Chapter 9 Troubleshooting

  2. Objectives • Describe the troubleshooting process • Describe the utilities used to verify TCP/IP connectivity • Identify & describe common hardware and connection issues in wired and wireless networks • Use the troubleshooting process to document problems and interact with a help desk

  3. Troubleshooting Process

  4. Troubleshooting • Identifying, locating and correcting problems • Not a trial & error! • Too much wasted time • Take documentation • The problem • Steps taken to determine the cause of the problem • Steps to correct the problem & ensure it won’t reoccur • Solutions that didn’t work • Solution that does work

  5. Effective Troubleshooting • 90% of your job!!! • JOB SECURITY if you do it good • Keeps users happy when working • If you get a help desk call… • You need a plan!

  6. Step 1: Gather Info • Verify problem • GATHER INFO • Question users • What happened? Any error messages? What web site did you type in? • COLLECT INFO • What equipment is involved? • Any recent changes to config? • Gather brand/model, warranty info • Gather network info • In you have tools, monitor network for errors

  7. Scenario • PC is down. • Need to finish sales report they were working on & it’s due at 11am. • Now what??? • What could the problems be? • Ask questions, narrow choices

  8. Troubleshooting Method 1 • Top-down • Application layer down • Starts near the user • Looking for problems in applications • Maybe a configuration problem in IE • Is it just one application that is not functioning, or do all applications fail? • For example, can the user access various web pages on the Internet, but not email? • Do other workstations have similar issues?

  9. Troubleshooting Method 2 • Bottom-up • Starts at Physical layer & then up • Good for novice • Could take longer to solve problems • Hardware & wires • Have cables been pulled out of their sockets? • If the equipment has indicator lights, are they on or off?

  10. Troubleshooting Method 3 • Divide-and-conquer • More experienced people • Start at middle layers & work up/down from there • Check IP address, default gateway

  11. Troubleshooting Method 4 • Trial & Error • Make an educated guess based on past experience • If doesn’t work, you use that info to try something else • Relies on your abilities & experience • This actually could slow you down

  12. Troubleshooting Method 5 • Substitution • Problem is specific to a piece of hardware • Can save time for user • You must have the available parts • Could be expensive • Doesn’t always happen

  13. At Home • Would you keep spare equipment, like an extra router? • Would you be running network monitors? • Should you keep documentation of problems, upgrades & software versions?

  14. Question • You get a call from your boss saying that he can not get access to the McDonalds web site. Which option would you do first? • Call McD’s & ask them to reboot their web server. • Get the boss a new NIC. • Have the boss to log off and log on again. • Ask the boss to read the web address he typed and what error message displayed.

  15. Activity

  16. Review • You complain to Comcast about connectivity issues. They are sending you a new cable modem. Which troubleshooting process is this? • Substitution • Bob’s PC is the only one in the office that can’t connect to the Internet. You are smart & use Divide & Conquer. What would you check first? • IP address configuration

  17. Review • Which of these would be best for a home network? • Having an extra Linksys router as backup • Keeping spare wireless cards handy • Keeping a backup of ISR configuration • Which of these is a physical layer problem? • Loose connectors • Wrong IP address • Driver not installed

  18. Troubleshooting Issues

  19. Let’s Get Physical! • Many problems are hardware related • Use your senses • Vision, smell, touch and hearing

  20. Utilities!

  21. Could it be a DHCP issue? • Ipconfig • Ipconfig /all, release, renew

  22. Activity- Using ipconfig • Packet Tracer Lab, 9.2.3.2

  23. May I Ping You? • Ok, you have an IP • Can you ping something? • Can also test DNS (ping www.cisco.com) • Echo request & reply

  24. Now What? • You have an IP • You can ping the destination • Must be a problem in the application • Like IE • You have an IP • You can NOT ping • Start pinging closer to you • Try default gateway 1st • YES: problem in not local • NO: problem is in local network

  25. Ping Example

  26. Ping Options

  27. Activity- Using Ping • Packet Tracer Lab 9.2.4.3

  28. Tracert • Shows path of routers (hops) • Can identify where the error is • 30 hops max; you can change • -h

  29. Netstat • Shows protocols used, port number, local & foreign address

  30. Nslookup • Is the DNS server properly translating names to IP addresses?

  31. Connectivity Issues

  32. More Issues • Wired & Wireless • Is the problem the wired or wireless? • Ping from each PC to DG & to each other • Check the Router

  33. Router/AP • Check the LED or status page

  34. Check the Cables! • Straight-through, crossover? • Bad connection? • Too long?

  35. What’s Wrong Here?

  36. WLAN Problems • a/b/g/n compatibility • Signal strength • Interference • SSID, Authentication, Encryption= MATCH! • SSID case sensitive • Keys don’t match • # of clients to channels • Do 9.3.4.2 & 9.3.5.2 Packet Tracer

  37. What’s Wrong Here?

  38. Activity

  39. Your LAN works, but… • No ISP connection • Check modem • Ping web site • Ping another web site • Are any access-lists set up?

  40. Review • Identify what each test does. • Ping • Tracert • Nslookup • Ipconfig • Something’s wrong. You check the cables first and they are bad. Which troubleshooting method did you use? • Bottom-up

  41. Review • The Linksys ISR is showing a blinking green LED on #1. What does that mean? • Activity…good!

  42. Troubleshooting & the Help Desk

  43. SOS • Other resources of help

  44. Help Desk • Provides assistance to determine if a problem exists, the nature of the problem, and the solution. • Can run remote diagnostics • Get all their info & document • What solved problem • What steps worked & didn’t work

  45. Baseline • When it all works… • Establish a baseline • What is normal traffic, etc. • Document it • After you make network changes, test again • Re-document the baseline

  46. Review- 10 Questions

  47. Fundamentals of Networking Discovery 1, Chapter 9 Troubleshooting

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