Transcript Discovery 1 Chapter 9 2007

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!!!
– 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 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
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