5.7 Given a scenario, troubleshoot problems with wired & wireless networks Flashcards
First step in troubleshooting Ethernet workstation connectivity issues?
Ensure patch cords are correctly connected & terminated
Substitute with a known good cable if necessary
How can you test transceivers if a loopback tool is not available?
Connect a different computer to the link or swap ports at the switch
However this may impact the network
When troubleshooting Ehternet workstation connectivity issues, what should you do if patch cords & network ports/NICs are not faulty?
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
How should Ethernet speed/duplex settings on switch interfaces & NICs typically be set?
To autonegotiate
What does port flapping mean?
NIC/switch interface repeatedly connects & disconnects
3 common causes of port flapping?
- Bad cabling
- External interference
- Faulty NIC at host end
How to identify port flapping using a switch?
Use switch configuration interface to track port uptime
What are the symptoms of intermittent connectivity?
Network connection repeatedly connects & disconnects
What can reduce the transfer speed of a cabled link?
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.
What should you check first if a user reports slow network speed?
Identify their network activity & confirm the link speed
4 external factors that can cause interference affecting network cabling?
- Power lines
- Fluorescent lighting
- Motors
- Generators
What is crosstalk?
Interference caused by poorly installed cabling & connector termination
When diagnosing network speed issues, what should you do if cabling is not the issue?
Update network adapter driver & check impact on other hosts with same NIC/driver
How can you determine the scope of a network speed problem?
See if issue affects 1 user, all switch-connected users, or all internet-connected users
What might cause network-wide congestion?
Fault or user behavior
user behavior like transferring a large amount of data over the network
What should you do first if you experience intermittent wireless connectivity?
Move both devices closer
What should you check if moving devices closer doesn’t solve wireless connectivity issues?
Ensure security & authentication settings are correct on both devices
What might cause an SSID to not appear in the list of available networks?
User could be out of range or the SSID broadcast is suppressed
What to do if an SSID broadcast is suppressed?
Manually configure the connection to the network
What is a standards mismatch in wireless networking?
AP isn’t in compatibility mode
So its unable to communicate with devices using older standards
How can devices using older 802.11 standards affect network performance?
Slows down the network due to AP having to use legacy frames
This adds overhead
Why might a device be unable to connect to a 5GHz network?
Device may only support 2.4GHz band
What is RSSI (Received Signal Strength Indicator)?
Measure of the signal strength
What will a wireless adapter do if the signal strength (RSSI) is not high enough?
RSSI = Received Signal Strength Indicator
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.
What may a wireless adapter do if the RSSI (signal strenth) is too low?
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’)
What could cause a weak/intermittent Wi-Fi connection within the supported range?
Interference from radio sources, electromagnetic sources, or physical objects
i.e. interference from motors & microwaves
How to reduce interference from other radio sources?
Adjusting the Wi-Fi channel that the devices use
5 materials that can block/degrade Wi-Fi signals?
- Metal
- Wire mesh
- Foil-backed plasterboard
- Concrete
- Mirrors
How does ordinary data transfer differ from real-time data transfer?
Prioritizing speed & can tolerate delays
How does real-time data transfer differ from ordinary data transfer?
Sensitive to delays & packet order
What is latency?
Time it takes for a signal to reach the recipient
What is the max one-way latency VoIP can support?
About 150ms
What is jitter?
Variation in delay over time
What causes jitter?
Network congestion affecting packet processing
on routers & switches
How much jitter can VoIP tolerate without severe impact on call quality?
Up to around 30ms
What does QoS (Quality of Service) do for VoIP traffic?
Prioritizes VoIP data over other types of data for better call quality
How to configure QoS on a SOHO network?
Use QoS/bandwidth control on router/modem to prioritize VoIP app port
What does a Limited connectivity message in Windows indicate?
Host physically connected to network but hasn’t receive IP config from DHCP server
What IP address range is used by Windows when it can’t get an IP address from DHCP server?
APIPA range (169.254.x.y)
When troubleshooting Windows Limited connectivity issues, what should you check if multiple users experience limited connectivity?
Check DHCP server
The issue likely lies there
What might cause a delay in recognizing DHCP server issues?
DHCP lease renewal times
Problems might take hours to manifest
What does it mean if Windows reports no internet access?
Netowrk adapter has IP config but can’t reach internet, suggesting a router/DNS issue
How can VLAN misconfiguration affect connectivity?
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.
