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Troubleshooting Performance Issues Flashcards

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1
Q

Occurs when two hosts on the network transmit at the same time which causes the signals to combine on the network medium

A

Collision

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2
Q

Collisions occur in both wired and wireless networks

A

To prevent collisions, design the networks with smaller collision domains

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3
Q

Network segment where simultaneous data transmissions collide with one another

A

Collision Domain

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4
Q

Occurs when a network system is overwhelmed by continuous multicast or broadcast traffic

A

Broadcast Storm

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5
Q

A broadcast storm significantly decreases network performance

A
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6
Q

A logical division of a computer network where all nodes can reach each other by broadcast at the data link layer

A

Broadcast Domain

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7
Q

A switch and a Layer 2 device will not break up broadcast domains because they bridge these things together.

A

Router or a layer 3 switch to break up the broadcast domain

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8
Q

Couple of main causes for broadcast storms occurring in your network

A
  1. Too large singular broadcast domain
  2. Large volume of DHCP requests
  3. Loops are created in the switching environment | enable bridge protocol data units (BPDU) on managed switches enforce a maximum number of MAC addresses per port, break up large broadcast domains into smaller domains using routers and layer 3 switches
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9
Q

Use a router to break up subnets into separate broadcast domains

A
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10
Q

How can you identify if you’re having a boradcast storm?

A

A rapid increase beyond the normal baseline may indicate a broadcast storm | during a broadcast storm, network devices struggle to process the flood of packets | wireshark & tcpdump

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11
Q

What is a network collision?

A

A: A collision occurs when data transmissions interfere on the physical medium, preventing data from reaching its destination.

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12
Q

Q: What is the most common cause of collisions?

A

A: Two hosts transmitting simultaneously on a shared medium, causing signals to overlap and become unreadable.

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13
Q

Q: Can collisions occur on both wired and wireless networks?

A

A: Yes, collisions can occur on both wired Ethernet and wireless networks.

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14
Q

Q: What Ethernet mechanisms handle collisions?

A

A: CSMA/CD (wired Ethernet) and CSMA/CA (wireless networks).

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15
Q

Q: What is a collision domain?

A

A: A network segment where simultaneous transmissions can collide due to shared access to the medium.

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16
Q

Q: How do hubs affect collision domains?

A

A: All devices connected to a hub share a single collision domain.

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17
Q

Q: How do wireless access points affect collision domains?

A

A: All connected wireless devices share the same collision domain.

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18
Q

Q: How can collision domains be reduced?

A

A: By using Layer 2 devices such as switches or bridges.

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19
Q

Q: How do switches prevent collisions?

A

A: Each switch port creates its own collision domain, preventing collisions between connected devices.

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20
Q

Q: How do collisions impact network performance?

A

A: Collisions force retransmissions, causing exponential degradation of throughput.

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21
Q

Q: Why do collisions cause retransmissions?

A

A: Devices back off using random timers and resend frames after detecting a collision.

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22
Q

Q: What is the first sign of excessive collisions?

A

A: Degraded network performance.

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23
Q

Q: How can collisions be detected on network devices?

A

A: By using the show interface command and reviewing interface statistics.

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24
Q

Q: What does an increasing collision counter indicate?

A

A: Collisions are occurring; this is expected on hubs but not on switched networks.

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25
Q: What does the deferred counter represent?
A: Frames delayed because the carrier was busy on the first transmission attempt.
26
Q: Is a rising deferred counter normal on switches?
A: No, it typically indicates a problem in switched networks.
27
Q: Is a rising deferred counter normal on hubs?
A: Yes, it is expected behavior.
28
Q: What is a late collision?
A: A collision detected after 5.12 microseconds (after the 512th bit is sent).
29
Q: What usually causes late collisions?
A: Incorrect cabling, faulty NICs, or excessive hub usage.
30
Q: Do late collisions indicate the root cause?
A: No, they indicate a problem but not its exact cause.
31
Q: What are excessive collisions?
A: Occur when a device exceeds the maximum of 16 retransmission attempts and drops the frame.
32
Q: Common causes of excessive collisions?
A: Full-duplex devices on shared media, faulty NICs, or too many devices in one collision domain.
33
Q: How can excessive collisions be resolved?
A: Disable auto-negotiation, lower speed, and configure half-duplex mode.
34
Q: What is a broadcast storm?
A: A condition where excessive broadcast or multicast traffic overwhelms the network.
35
Q: How do wireless access points affect collision domains?
A: All connected wireless devices share the same collision domain.
36
Q: How can collision domains be reduced?
A: By using Layer 2 devices such as switches or bridges.
37
Q: How do switches prevent collisions?
A: Each switch port creates its own collision domain, preventing collisions between connected devices.
38
Q: How do collisions impact network performance?
A: Collisions force retransmissions, causing exponential degradation of throughput.
39
Q: Why do collisions cause retransmissions?
A: Devices back off using random timers and resend frames after detecting a collision.
40
Q: What is the first sign of excessive collisions?
A: Degraded network performance.
41
Q: How can collisions be detected on network devices?
A: By using the show interface command and reviewing interface statistics.
42
Q: What does an increasing collision counter indicate?
A: Collisions are occurring; this is expected on hubs but not on switched networks.
43
Q: What does the deferred counter represent?
A: Frames delayed because the carrier was busy on the first transmission attempt.
44
Q: How do large broadcast domains cause storms?
A: Too many devices generate excessive broadcast traffic.
45
Q: Why are large Class B networks problematic?
A: They can contain up to 65,534 hosts in one broadcast domain.
46
Exam Takeaways (High-Yield)
Hubs = single collision domain; switches = one collision domain per port Collisions should not occur in properly switched networks Late and excessive collisions indicate physical or duplex issues Broadcast storms overwhelm switches and cause denial of service Switches do NOT break broadcast domains; routers do Large networks must be subnetted to reduce broadcasts DHCP Discover messages are broadcasts Switching loops are a major cause of broadcast storms Spanning Tree (BPDUs) is critical for loop prevention
47
Set of protocols that are used to send streaming voice and video in real time
Voice Over Internet Protocol (VoIP)
48
Two major quality issues with VOIP:
Latency - Time it takes for a signal to reach the intended client Jitter - Measurement of the variation in delay over time Increase network performance Implement quality of service -settings only affect things inside the network | settings the quality of service (QoS) allows prioritization of voice traffic
49
Occurs when data packets traveling across a network fail to reach their intended destination
Packet Loss
50
Come problems from packet loss:
Unexplained network slowdowns Jitter during VoIP calls Abrupt disconnections in streaming media playback
51
Causes of packet loss
Network congestion - Occurs when too much data is sent through a network that exceeds the networks' handling capacity | traffic jam Faulty router configurations - Occurs when routers are set up incorrectly and lead to data being misdirected or not prioritized properly by the systems | bad directions Bad cables - Physically damaged or deteriorating wires that will disrupt the network's data transmission | leaking pipe under my bathroom sink Hardware failures - Occurs when network devices like switches, routers, or modems malfunction
52
Used to map the path that data will take to reach its intended destination
Traceroute
53
Provides comprehensive insights into traffic patterns to help pinpoint the exact location and the potential cause of the packet loss
Network Monitoring
54
Ways to solve packet loss
Network Congestion Issue - Increase bandwidth Optimize network layout Employ QoS Hardware Issue - Routine inspection/ Replace faulty cables, update firmware to resolve any known issues Configuration Errors - Verify configuration settings Incorrect Settings - Properly configure device implement proactive measures to help prevent packet loss Maintain a well-documented network configuration policy to prevent misconfigurations
55
5 most common causes of network performance issues
high cpu usage - increases latency, jitter, and packet loss | upgrade your network devices to more powerful ones, simplifty processing load high bandwidth usage - network communications have to wait to enter or leave that network | increase your bandwidth size by paying more to your ISP poor connectivity - poor physical connection | check cables and test them one by one/ test client to the demarcation point | test demarcation point > border router > switch >client | use a cable tester for twisted pair connections or a fiber light meter for fiber optic connections network malfunction - Use the seven step troublshooting method to find the device/configuration issue/hardware failure issue DNS problems - high DNS latency = slow down the overall user experience | user requests a website
56
Calculation that considers all the anticipated losses along the length of a fiber optic connection | reduced transmission, slow connection speeds, connection downtime
Optical Link Budget
57
0.25 dB per km for a standard fiber optic cable
58
Used as a credential to facilitate verification of identities between users in a transaction
Digital Certificate
59
Determine the license Compare the license vs. features Contact the manufacturer
60
BYOD
Decrease in capital expenditures Increase in Operational Expenitures
61
Hardware failures
Replace the failed component Replace the entire device Return to the manufacturer for repair or properly dispose
62
You get several emails from co-workers experiencing intermittent disruptions in their video conference calls. They note occasional freezes and audio delays, but otherwise seem to be functioning normally. What is the most likely cause of this issue?
Jitter
63
Which of the following will occur when a network is overwhelmed by continuous multicast traffic?
Broadcast storms
64
On a university campus, students living in dormitories often complain about sluggish internet speeds, especially during evenings when many are simultaneously online. Despite having a robust internet infrastructure, students report difficulty in accessing online lectures and submitting assignments on time due to the slow connection. Moreover, the university's IT department notices a significant spike in network traffic during these peak hours. What is the most likely cause of the slow internet speeds experienced by students in the dormitories?
Network congestion
65
In a network environment, users report experiencing sluggish internet speeds and intermittent connectivity. Upon investigation, it's discovered that a router is encountering severe congestion, leading to performance degradation. What is the most likely cause of the network performance issue?
Packet loss - the router is likely dropping packets due to high traffic volume, directly leading to the reported sluggishness and intermittent connecvitivity
66
Which of the following commands would help to determine where packets are being lost?
Traceroute
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