5.7 Given a scenario, troubleshoot problems with wired & wireless networks

Question 1

First step in troubleshooting Ethernet workstation connectivity issues?

Answer 1

Ensure patch cords are correctly connected & terminated

Substitute with a known good cable if necessary

Question 2

How can you test transceivers if a loopback tool is not available?

Answer 2

Connect a different computer to the link or swap ports at the switch

However this may impact the network

Question 3

When troubleshooting Ehternet workstation connectivity issues, what should you do if patch cords & network ports/NICs are not faulty?

Answer 3

Use cable tester to verify the structured cabling

Use a certifier for detailed performance & interference information

If that doesnt work, update the NIC’s device driver software

Question 4

How should Ethernet speed/duplex settings on switch interfaces & NICs typically be set?

Answer 4

To autonegotiate

Question 5

What does port flapping mean?

Answer 5

NIC/switch interface repeatedly connects & disconnects

Question 6

3 common causes of port flapping?

Answer 6

• Bad cabling
• External interference
• Faulty NIC at host end

Question 7

How to identify port flapping using a switch?

Answer 7

Use switch configuration interface to track port uptime

Question 8

What are the symptoms of intermittent connectivity?

Answer 8

Network connection repeatedly connects & disconnects

Question 9

What can reduce the transfer speed of a cabled link?

Answer 9

Mismatched duplex settings on the network adapter & switch port

Mismatched duplex settings between the network adapter and switch port can lead to data collisions and retransmissions, slowing down transfer speeds on the link.

Question 10

What should you check first if a user reports slow network speed?

Answer 10

Identify their network activity & confirm the link speed

Question 11

4 external factors that can cause interference affecting network cabling?

Answer 11

• Power lines
• Fluorescent lighting
• Motors
• Generators

Question 12

What is crosstalk?

Answer 12

Interference caused by poorly installed cabling & connector termination

Question 13

When diagnosing network speed issues, what should you do if cabling is not the issue?

Answer 13

Update network adapter driver & check impact on other hosts with same NIC/driver

Question 14

How can you determine the scope of a network speed problem?

Answer 14

See if issue affects 1 user, all switch-connected users, or all internet-connected users

Question 15

What might cause network-wide congestion?

Answer 15

Fault or user behavior

user behavior like transferring a large amount of data over the network

Question 16

What should you do first if you experience intermittent wireless connectivity?

Answer 16

Move both devices closer

Question 17

What should you check if moving devices closer doesn’t solve wireless connectivity issues?

Answer 17

Ensure security & authentication settings are correct on both devices

Question 18

What might cause an SSID to not appear in the list of available networks?

Answer 18

User could be out of range or the SSID broadcast is suppressed

Question 19

What to do if an SSID broadcast is suppressed?

Answer 19

Manually configure the connection to the network

Question 20

What is a standards mismatch in wireless networking?

Answer 20

AP isn’t in compatibility mode

So its unable to communicate with devices using older standards

Question 21

How can devices using older 802.11 standards affect network performance?

Answer 21

Slows down the network due to AP having to use legacy frames

This adds overhead

Question 22

Why might a device be unable to connect to a 5GHz network?

Answer 22

Device may only support 2.4GHz band

Question 23

What is RSSI (Received Signal Strength Indicator)?

Answer 23

Measure of the signal strength

Question 24

What will a wireless adapter do if the signal strength (RSSI) is not high enough?

RSSI = Received Signal Strength Indicator

Answer 24

Lower connection speed

For example, an 802.11n adapter might support up to 144Mbps with a strong signal, but if the signal is weak, the speed may drop to 54Mbps or even 11Mbps to maintain a reliable connection.

Question 25

What may a wireless adapter do if the RSSI (signal strenth) is too low?

Answer 25

Drop connection & try to connect to a different network

If there’s multiple networks, the adapter might switch between them, causing instability (known as ‘flapping’)

Question 26

What could cause a weak/intermittent Wi-Fi connection within the supported range?

Answer 26

Interference from radio sources, electromagnetic sources, or physical objects

i.e. interference from motors & microwaves

Question 27

How to reduce interference from other radio sources?

Answer 27

Adjusting the Wi-Fi channel that the devices use

Question 28

5 materials that can block/degrade Wi-Fi signals?

Answer 28

• Metal
• Wire mesh
• Foil-backed plasterboard
• Concrete
• Mirrors

Foil-backed plasterboard

Question 29

How does ordinary data transfer differ from real-time data transfer?

Answer 29

Prioritizing speed & can tolerate delays

Question 30

How does real-time data transfer differ from ordinary data transfer?

Answer 30

Sensitive to delays & packet order

Question 31

What is latency?

Answer 31

Time it takes for a signal to reach the recipient

Question 32

What is the max one-way latency VoIP can support?

Answer 32

About 150ms

Question 33

What is jitter?

Answer 33

Variation in delay over time

Question 34

What causes jitter?

Answer 34

Network congestion affecting packet processing

on routers & switches

Question 35

How much jitter can VoIP tolerate without severe impact on call quality?

Answer 35

Up to around 30ms

Question 36

What does QoS (Quality of Service) do for VoIP traffic?

Answer 36

Prioritizes VoIP data over other types of data for better call quality

Question 37

How to configure QoS on a SOHO network?

Answer 37

Use QoS/bandwidth control on router/modem to prioritize VoIP app port

Question 38

What does a Limited connectivity message in Windows indicate?

Answer 38

Host physically connected to network but hasn’t receive IP config from DHCP server

Question 39

What IP address range is used by Windows when it can’t get an IP address from DHCP server?

Answer 39

APIPA range (169.254.x.y)

Question 40

When troubleshooting Windows Limited connectivity issues, what should you check if multiple users experience limited connectivity?

Answer 40

Check DHCP server

The issue likely lies there

Question 41

What might cause a delay in recognizing DHCP server issues?

Answer 41

DHCP lease renewal times

Problems might take hours to manifest

Question 42

What does it mean if Windows reports no internet access?

Answer 42

Netowrk adapter has IP config but can’t reach internet, suggesting a router/DNS issue

Question 43

How can VLAN misconfiguration affect connectivity?

Answer 43

Incorrect VLAN ID can hinder host from accessing correct network services

Incorrect VLAN ID on a host can prevent communication with devices and services in the intended VLAN, causing connectivity issues and restricting access to necessary network resources.