9: Troubleshooting Your Network Networking for Home & Small Business
I Want My Network! Troubleshooting process Utilities for connectivity tests Common hardware & connection issues Working with the help desk
Troubleshooting Identifying, locating and correcting problems Not a trial & error! Too much wasted time Take documentation The problem encountered Steps taken to determine the cause of the problem Steps to correct the problem and ensure that it will not reoccur
Step 1 Verify problem & GATHER INFO Question users What happened? Any error messages? What web site did you type in? 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
Why do this? 90% of your job!!! If you get a help desk call… JOB SECURITY Keeps users happy when working If you get a help desk call… You need a plan!
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? Now compare to the OSI model
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?
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?
Troubleshooting Method 3 Divide-and-conquer More experienced people Start at middle layers & work up/down from there Check IP address
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
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
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?
Activity
Let’s Get Physical! Many problems are hardware related Use your senses Vision, smell, touch and hearing
Utilities!
Could it be a DHCP issue? Ipconfig Ipconfig /all, release, renew
Activity Packet Tracer Lab, 9.2.3.2
May I Ping You? Ok, you have an IP Can you ping something? Can also test DNS (ping www.cisco.com)
Now What? You have an IP You can ping the destination Must be a problem in the application Like IE You can NOT ping Start pinging closer to you Try default gateway 1st YES: problem in not local NO: problem is in local network
Ping Example
Ping Options
Activity Packet Tracer Lab 9.2.4.3
Tracert Shows path of routers (hops) Can identify where the error is 30 hops max; you can change -h
Netstat Shows protocols used, port number, local & foreign address
Nslookup Is the DNS server properly translating names to IP addresses?
More Issues Wired & Wireless Ping from each to DG & to each other Check the Router
Router/AP Check the LED
Check the Cables! Straight-through, crossover? Bad connection? Too long?
What’s Wrong Here?
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
What’s Wrong Here?
Activity
Your LAN works, but… No ISP connection Check modem Ping web site Ping another web site Are any access-lists set up?
SOS Other resources of help
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
9: Troubleshooting Your Network Networking for Home & Small Business