Lesson 4 - Chapter 5: Troubleshooting Networks Flashcards
Someone yells, “The network is down!” What’s the first place you should start troubleshooting?
start at the physical level to rule out connectivity as the source of the problem
When a Windows PC is connected to a wired network, how does it appear in the notification area?
It shows up as a monitor with a cable next to it
When a Windows PC is disconnected from a wire network, what does the icon look like in the notification area?
A globe with a crossed-out “no” symbol
If you see the globe icon for a wired connection, what are 2 obvious things to check?
- Is a cable unplugged or damaged at any point?
- Is the switch or router powered up and operational?
If you see the globe icon for a wired connection, after checking the 2 obvious things, what basic troubleshooting do you perform next?
Reboot everything (PC, switch or router, and cable modem)
With physical LAN connectivity issues, after checking obvious things and rebooting when you see the global icon, what’s the next step in checking for hardware problems?
Check the link lights on the NIC and switch to see if they’re lit (or ask the user to check the lights for you)
What’s a question to ask yourself when determining the scope of the problem?
Is it just this PC or all PCs connected to the same switch/router having an issue?
Multiple PCs failing to access the network often points to what kind of problems?
often points to hardware problems at the switch/router (or server if it’s a domain-based network)
What do you check if the network fails in an office with a structured cabling system?
Determine if the wall outlet or its cabling is faulty by connecting the no-network system’s NIC directly to a known-good network port in another office to see if it works with a tech’s own long patch cable
(if network connectivity works, suspect the patch cable running from the first outlet to the switch)
A bad ___ can cause a lack of connectivity
a bad NIC
What are 4 ways to use software to troubleshoot a bad NIC? Windows and macOS
- Windows: Device Manager > Check NIC’s status
- Windows: Network Troubleshooter utility (Find and Fix Network Problems)
- macOS: Apple > System Settings > Network > Check status
- NIC came with diagnostic software? Run it
What part of a NIC is a common failure point?
the NIC’s female connector
NICs that come with diagnostic software often include a special test called what?
often include a special test called loopback test
What’s a loopback test?
it tests the NIC by sending data out of the NIC and checks to see if it comes back
(some NICs perform only an internal loopback which tests the circuitry not the connection pins)
What’s a loopback plug?
A plug inserted into the NIC’s port in order to do a true external loopback test
What do you do if the NIC is bad? (2)
- Replace it
- If built into the motherboard, disable it in BIOS/UEFI and replace it with a PCIe or USB model
How do you diagnose bad horizontal cabling run, and whether the cable is disconnected and where?
with a mid-range time-domain reflectometer (TDR) tester
(such as the Fluke Microscanner)
What does a time-domain reflectometer (TDR) tester measure?
it measures impedance in network cabling
(if it measures any impedance, something is wrong with the cable)
How do you use a TDR tester?
You unplug the patch cable from the PC, and attach the tester OR you unplug the patch cable from the switch and plug the tester into that patch cable (complete test this way)
What do you do if horizontal cabling is bad?
Call your local installer. If it’s bad in one spot, it’s probably bad in another and needs replacement.
What does it mean to trace cables?
identify
What device do you use to trace cables?
toner
What is toner?
a generic term for 2 separate devices that are used together
What are the 2 separate devices that are used together to trace cables?
- Tone Generator
- Tone Probe
(a popular device brand name for these is Fox and Hound)
What are 2 possible meanings for a loss in connectivity?
- Loss of physical hardware (cabling, switch, router, server, outlet, etc)
- Loss of connectivity to a specific resource
When you can’t connect to a resource on the first try, it often points to what?
a configuration issue
(have the right share name? username/pass? permission? right domain/workgroup? printer/folder isn’t shared or doesn’t exist on that server?)
What are 4 things to check if you can’t access a previously accessed resource?
- Can you
- Is the
- Is your
- Can others
- Can you see it in File Explorer under Network?
- Is the serving system on?
- Is your computer physically connected to the serving system?
- Can others access it? Did someone lose permission to access it?
What does the “net” command allow you to do? W
view a network quickly (comes with many options)
(good for when you first plug into a network and don’t know the names of other computers on the network)
What does the “net view” command allow you to do? W
returns a list of Windows computers on the network
(command-line version of browsing the network using File Explorer)
What command shows any shares on a particular machine and whether they are mapped drivers?
net view [computer name]
What is the “net use” command?
command-line method for mapping network shares
(like mapping the Research share to the X: drive)
C:>net use x: \server1\research
What command lists all the user accounts on the PC and can be used to create new user accounts on the local computer and domain?
net user
To see existing user accounts, what command do you use?
net user (without switches)
C:>net user
How do you create a new account on the local computer and domain? What command and switch do you use?
Create the user tomsmith, password hard2guess
C:>net user tomsmith hard2guess /add /domain
How do you delete a user account?
Delete the user tomsmith
C:>net user tomsmith /delete
To take a quick glance at your network settings, what command do you use?
ipconfig
What command do you use to see network settings in more details?
ipconfig /all
What is the macOS/Linux equivalent of ipconfig?
ip
What command do you use to release and renew your IP address? What would that syntax look like to renew and release it? (3)
[this is for when you’re using DHCP]
- ipconfig
renew = ipconfig /renew
release = ipconfig /release
(ipconfig /? for a list of available switches)
What does the “nslookup” command do?
enables you to determine exactly what information the DNS server is giving you about a specific host name
What does the ping command allow you to do?
lets you see if you can talk to another system
How do you use the ping command?
ping www.google.com
(shows you how long it take to get a response)
What are 2 switches you can use with “ping”?
-t which sends ping packets continuously until you stop it with CTRL+C
-l which enables you to specify how big a ping packet to send (el switch)
What is tracert used as on macOS and Linux?
on macOS and Linux, the tracert utility is traceroute
What does the tracert or traceroute utility do?
It shows the route a packet takes to get to its destination
(devices it passes, how long each hop between is)
How do you use tracert/traceroute?
example
tracert [IP address or URL]
How would a user trace the route to their own ISP?
they would do
tracert [default gateway IP address of the LAN’s router]
the default gateway is the path out to the Internet remember
What command would come in handy when you need to troubleshoot bottlenecks (difficulty reaching a destination)?
tracert/traceroute (macOS/Linux)
to see if the problem is a machine or connection you have control over
What does the “pathping” command in Windows do?
it combines the functions of ping and tracert (traceroute) in a single command
it sends echo requests to each router (like ping) and evaluates the speed packets are returned (like tracert) and tracks packet losses from each router which helps you find which router is having issues
What is the Linux equivalent of pathping?
mtr
What command shows current active network connections and protocol statistics?
netstat
What does the netstat command show when used without switches?
it scans the network and reports all the IP addresses involved in connections
(like how your PC is communicating with various websites which can be identified by the “https”)
Do “netstat” switches use a hyphen or a slash?
the netstat switches use a hyphen rather than a slash
netstat -s
(reports network stats)
What command do you use to determine whether a particular IP address was reachable?
ping
To test an RJ-45 port, use a ___ ___
loopback plug
To test a cable, use a ___ ___
cable tester
To trace a cable, use a ___ ___ and a ___
use a tone generator and a probe
