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CompTIA Network+ > Section 5: Network Troubleshooting > Flashcards

Section 5: Network Troubleshooting Flashcards

1
Q

What is the first step in the troubleshooting process?

A

Identify the Problem

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2
Q

After identifying the problem, what is the next step in troubleshooting?

A

Establish a theory of probable cause

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3
Q

After establishing a theory of probable cause, what is the next step?

A

Test the Theory

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4
Q

Once the theory is confirmed, what is the next step?

A

Establish a plan of action

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5
Q

After establishing a plan of action, what is the next step?

A

Implement the solution

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6
Q

After implementing the solution, what is the next step?

A

Verify full system functionality, if applicable install preventive measures.

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7
Q

After verifying full system functionality, what is the next step?

A

Document findings and actions

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8
Q

What are common cable issues, and how can incorrect cables cause problems?

A
  1. Single Mode vs. Multimode Fiber: Using the wrong type can cause mismatched connections and poor performance.
  2. Category 5/6/7/8: Lower-category cables may not support higher bandwidths or frequencies.
  3. STP vs. UTP: Incorrect use can result in inadequate shielding and increased interference.
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9
Q

What are 3 common causes of signal degradation in cables?

A

Crosstalk: Signals interfere between adjacent cables, often caused by poor cable design or installation.

Interference: External electromagnetic interference (EMI) from devices or power lines.

Attenuation: Signal weakening over long distances or through poor-quality cables.

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10
Q

What is improper termination, and how does it affect networks?

A

Terminating cables incorrectly (e.g., poor crimping, incorrect pinouts) can cause data loss or connection instability.

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11
Q

What happens when TX/RX are transposed, and how can you fix it?

A

Issue: Transmitting and receiving wires are reversed, preventing communication.

Fix: Verify and correct the cable pinout or use a crossover cable if required.

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12
Q

What are interface issues indicated by increasing interface counters?

A

Cyclic Redundancy Check (CRC): Indicates data corruption during transmission.

Runts: Packets smaller than the minimum allowed size.

Giants: Packets exceeding the maximum allowed size.

Drops: Packets discarded due to buffer overflow or errors.

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13
Q

What are 3 common port status issues, and what do they mean?

A

Error Disabled: Port shut down due to detected issues (e.g., security violation).

Administratively Down: Port manually disabled by an administrator.

Suspended: Port inactive due to configuration or policy conflicts.

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14
Q

What are common hardware issues related to Power over Ethernet (PoE)?

A

Power Budget Exceeded: Insufficient power available for connected PoE devices.

Incorrect Standard: Device uses a PoE standard incompatible with the switch (e.g., IEEE 802.3af vs. 802.3at).

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15
Q

What are common transceiver issues, and how can they affect performance?

A

Mismatch: Incorrect transceiver type (e.g., single-mode used on a multimode connection).

Signal Strength Issues: Weak or poor-quality signal due to dirty connectors, long distances, or degraded optics.

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16
Q

What is the purpose of STP (Spanning Tree Protocol)?

A

Prevents network loops by creating a loop-free topology in Ethernet networks.
* Ensures redundancy while avoiding broadcast storms.

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17
Q

What are 4 common STP issues?

A
  1. Network Loops: Occur when STP is disabled or misconfigured, leading to broadcast storms.
  2. Root Bridge Selection: If the wrong switch becomes the root bridge, it can cause suboptimal paths.
  3. Port Roles: Incorrect roles (root, designated, or blocked) can affect traffic flow.
  4. Port States: Misconfigured port states (e.g., listening, learning, forwarding, or blocking) can delay convergence or cause outages.
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18
Q

What happens with an incorrect VLAN assignment, and how do you resolve it?

A

Issue: Devices assigned to the wrong VLAN cannot communicate with the intended network.

Resolution: Verify and correct VLAN configurations on switch ports and trunk links.

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19
Q

What issues can occur with Access Control Lists (ACLs)?

A

Incorrect ACL Rules: Can block legitimate traffic or allow unauthorized access.

Resolution: Review ACLs for proper source, destination, and protocol/port configurations.

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20
Q

What is a routing table, and why is it critical for route selection?

A

Routing Table: Contains information about network destinations and the best paths to reach them.

Issues:
* Missing or incorrect routes can prevent traffic from reaching its destination.
* Incorrect default routes can send traffic to the wrong next hop.

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21
Q

What happens with an incorrect default gateway configuration?

A

Devices cannot communicate outside their local subnet.

  • Resolution: Configure the correct gateway IP address on affected devices.
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22
Q

What is address pool exhaustion, and what causes it?

A

Definition: No available IP addresses for new devices.

Causes: Mismanaged DHCP scopes or too many devices on the network.

Resolution: Increase the DHCP scope or implement subnetting.

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23
Q

What are the impacts of an incorrect IP address or duplicate IP address?

A

Incorrect IP Address: Prevents devices from communicating on the network.

Duplicate IP Address: Causes conflicts, leading to intermittent or no connectivity for affected devices.

Resolution: Verify and assign unique, correct IP addresses to all devices.

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24
Q

What is congestion/contention, and how does it affect the network?

A

Congestion: Occurs when network traffic exceeds available resources, causing delays.

Contention: Multiple devices competing for the same resources.

Impact: Increased latency, packet loss, and reduced throughput.

25
Q

What is bottlenecking, and how can it be resolved?

A

Bottlenecking: A single device or link limits overall network performance.
* Fix: Upgrade the bottlenecked hardware (e.g., switches, routers) or optimize traffic flow.

26
Q

How do bandwidth and throughput capacity differ?

A

Bandwidth: Maximum theoretical data rate of a network connection.

Throughput Capacity: Actual amount of data successfully transmitted over the network.

Issue: Low throughput indicates inefficiencies or congestion.

Fix: Identify and resolve congestion, upgrade hardware, or implement Quality of Service (QoS).

27
Q

What is latency, and how can it be reduced?

A

Latency: The delay in data transmission between source and destination.
* Fix: Reduce hop counts, upgrade equipment, or optimize routing paths.

28
Q

What is packet loss, and what are common causes?

A

Packet Loss: Packets are dropped or fail to reach their destination.

Causes: Congestion, faulty cables, interference, or overloaded devices.

Fix: Identify and replace faulty hardware or optimize traffic flow.

29
Q

What is jitter, and why is it problematic?

A

Jitter: Variability in packet delay, often impacting real-time applications like VoIP.
* Fix: Implement QoS to prioritize real-time traffic and reduce variability.

30
Q

What are common wireless interference issues, and how can they be mitigated?

A

Channel Overlap: Adjacent access points using overlapping channels.
* Fix: Use non-overlapping channels (e.g., 1, 6, 11 on 2.4 GHz).

Other sources: Nearby electronics, walls, or microwave ovens.
* Fix: Relocate devices or switch to the 5 GHz or 6 GHz band.

31
Q

What causes signal degradation or loss, and how is it resolved?

A

Causes: Distance from the AP, physical obstructions, or interference.

Fix: Optimize AP placement, upgrade antennas, or use repeaters/extenders.

32
Q

What is insufficient wireless coverage, and how can it be fixed?

A

Issue: Dead zones where wireless signals cannot reach.

Fix: Add additional access points, mesh networks, or extenders to improve coverage.

33
Q

What are client disassociation issues, and how can they be addressed?

A

Issue: Devices disconnect frequently from the network.

Fix: Check for AP capacity limits, interference, or misconfigurations in power settings.

34
Q

What is roaming misconfiguration, and how does it affect users?

A

Issue: Devices fail to transition smoothly between access points.

Fix: Enable features like fast roaming (802.11r) or optimize AP power levels and channel selection.

35
Q

What does a protocol analyzer do?

A

It captures and analyzes network traffic to identify issues, monitor performance, or detect malicious activity. Example: Wireshark.

36
Q

What is Nmap used for?

A

Scans networks for open ports, services, and vulnerabilities.

37
Q

What is Link Layer Discovery Protocol (LLDP) or Cisco Discovery Protocol (CDP)?

A

Protocols used for device discovery on local networks, providing details like device type and IP address.

38
Q

What is a speed tester?

A

Measures the upload and download speeds of a network connection, often used to diagnose bandwidth issues.

39
Q

What does the ping command do?

A

Sends ICMP Echo Request packets to test connectivity to a remote host and measure round-trip time.

40
Q

What does the traceroute/tracert command do?

A

Displays the path packets take to reach a destination and identifies latency at each hop.

41
Q

What is the purpose of the nslookup command?

A

Queries DNS servers to resolve domain names into IP addresses or troubleshoot DNS issues.

42
Q

What is the purpose of the dig command?

A

Queries DNS servers to retrieve detailed information, such as A, MX, or TXT records.

43
Q

What does tcpdump do?

A

Captures and displays network packets in real time, often used for troubleshooting network issues.

44
Q

What does the netstat command show?

A

Displays network connections, routing tables, and protocol statistics.

45
Q

What is the function of the ip/ifconfig/ipconfig commands?

A

They display or configure IP address information on network interfaces.

ipconfig: Windows.
ifconfig/ip: Linux/Unix.

46
Q

What does the arp command do?

A

Displays or modifies the ARP table, which maps IP addresses to MAC addresses.

47
Q

What is a toner used for in networking?

A

Locates specific wires or cables within a bundle or wall using a signal tone.

48
Q

What does a cable tester do?

A

Tests the integrity of cables, checking for continuity, shorts, or incorrect wiring.

49
Q

What are taps in networking?

A

Hardware devices that passively copy network traffic for monitoring or analysis.

50
Q

What is the function of a Wi-Fi analyzer?

A

Scans wireless networks to identify signal strength, channel usage, and interference.

51
Q

What is a visual fault locator?

A

Uses visible light to identify breaks or faults in optical fiber cables.

52
Q

What does the show mac-address-table command do?

A

Displays the MAC address table of a switch, mapping MAC addresses to specific ports.

53
Q

What does the show route command display?

A

Displays the routing table, showing how packets will be forwarded through the network.

54
Q

What does the show config command display?

A

Shows the current configuration of a networking device.

55
Q

What is the purpose of the show interface command?

A

Displays detailed information about the status, speed, and errors of network interfaces.

56
Q

What does the show arp command do?

A

Displays the ARP table, showing IP-to-MAC address mappings.

57
Q

What does the show vlan command display?

A

Lists VLANs configured on a switch and their associated ports.

58
Q

What does the show power command do?

A

Displays power-related information, often for devices using Power over Ethernet (PoE).

CompTIA Network+ (6 decks)

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