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

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

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)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 1 st ▫ 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?

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!

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