S24 - Network Troubleshooting Flashcards
2 Main methods of checking if your NIC is working
Network cable tester & Look at back of NIC card: 3 lights will be there:
1) lack of link light, there is a physical issue somewhere along the path)
2) activity light will blink when sending and receiving data
3) present in some cards, will display what speed the card is running at, off if 10mbps, orange if 100mbps, green if 1000mbps
What piece of equipment can be used for extending the line
Repeater, increases the signal
Recommended type of cable if running past power lines, generators erc
Fibre, not twisted copper cable
Define Port Flapping
Caused by an intermittent connectivity issue between the client and network switch
Flapping status is
is constant switching of upstate to downstate
4 Main cable issues
Physical connection
Cable length
Interference
Port flapping
Define network performance issues
Manifesting the slow down of network
Define half duplex
Network that sends or receive information, Not both at the same time
Give an example of half duplex
Walky-talky communication
Define full-duplex
Network that sends or receives information at the same time
What mode are NICs set to in terms of half and full dupex
auto negotiation
Define data exfiltration
Sending data in the background without the user seeing it
4 things that can cause network connectivity issues
Mismatch in duplex settings
Mismatch in speed setting
Network adapter drivers are out of date
Malware Infection
3 Main groups for network troubleshooting to consider
Is this:
Single Client, Network segment or Entire Network
If single client issue we need to look at
Individual duplex settings, speed settings, network adapter drivers, malware
If Network Segment issue we need to look at
Look for single switch settings
If Entire network issue we need to look at
Look for the router, gateway, firewall
4 Things that can cause wireless connectivity issues
Intermittent wireless connectivity
Signal Interference
Low signal strength
Standards mismatch
Define intermittent wireless connectivity
connected or disconnected network
define intermittent wired connectivity
Upstate to a downstate of a switch port
Define signal interfernece
Something that is causing signal issues
Define Received signal strength Indicator (RSSI)
Used to measure the signal strength based on an index level and gives a value in decibels (dB)
RSSI is displayed in
Negative decibels
Things you can do to increase wireless signal strength
Increase power of transmission
Increase antenna size
Move closer to the source
2 things that can happen with low dB
Speed decreases, intermittent connectivity issues
To combat the auto config of speeds on the 2Ghz band where older devices are slowing everyone else down as the router has to modify the 2Ghz band for them, what can we do
Configure the WAP to support the modern versions of the protocols
Define Voice over internet protocol (VoIP)
Set of protocols that are used to send steaming voice and video in real time
Define latency
Time it takes for a signal to reach the intended client
With VoIP, recommended latency
50-100 milliseconds
Define jitter
Measurement of the variation in a delay over time
When does jitter happen
When latency increases by up to 30-50 milliseconds
What can we do to improve latency and jitter
Increase network performance
Implement quality of service (tool in network that allows for traffic prioritisation)
What does the Quality of Service (QoS) allow for VOIP
prioritisation of voice traffic
Define limited connectivity
Specialised message to receive within the OS
What 3 things to check when having limited connectivity
Affects one network or client
VLAN is properly configured
DHCP not working properly
Limited connectivity is linked to
DHCP issues
Define cross talk
caused by unintentional and undesired transmission of a signal from one cable to another
