troubleshooting

Question 1

7 step troubleshooting methodology:

Answer 1

1. identify the problem
2. establish theory of probable cause
3. test the theory to determine the cause
4. establish a plan of action to resolve the problem
5. implement the solution / escalate if necessary
6. verify full system functionality
7. document findings, actions, outcomes and lessons learned

Question 2

RSSI

Answer 2

Received Signal Strength Indication (RSSI): estimated strength of the wifi signal received by the client

anything from zero to minus 60dBm indicated good, strong signal

Question 3

EIRP

Answer 3

effective Equivalent isotropic radiated power
signal strength emitted by the access point
measured in dBi

Question 4

Channel utilisation for an efficient wifi network?

Answer 4

keep below 30%

Question 5

attenuation

Answer 5

reduction of signal strength between the transmission and receipt of the signal

Question 6

Users connecting to an SSID appear to be unable to authenticate to the captive portal. Which of the following is the MOST likely cause of the issue?

Answer 6

Captive portals usually rely on 802.1x, and 802.1x uses RADIUS for authentication. The IEEE 802.1x standard is a network authentication protocol that opens ports for network access when an organization authenticates a user’s identity and authorizes them for access to the network. This defines port security. The user’s identity is determined based on their credentials or certificate, which is confirmed by the RADIUS server.

Question 7

You are troubleshooting network connectivity issues for a large network. You determine you need to start troubleshooting beginning with the middle layer of the OSI model and moving up or down based on your findings. Which troubleshooting methodology are you using?

Answer 7

With the Divide and conquer troubleshooting approach, you start in the middle of the OSI model (network layer) and move up or down the layers based on what you think is causing the problem.

The Top-to-bottom approach begins on layer 7 (Application) and moves down to layers 6, 5, 4, and so on.

Question 8

What property is defined as a gradual reduction in signal strength with an increased distance from a source?

Answer 8

Attenuation is a natural property that occurs as a reduction of signal when the distance from the source increases.

EMI (Electromagnetic Interference) is a disturbance generated by an external source.

Crosstalk is a form of EMI in which one circuit creates an undesired effect on another.

Question 9

What is known as variance in delay?

Answer 9

Variance in Delay is known as Jitter which is measured in Milliseconds. Delay is the amount of time it takes for a packet to travel from one point to the next measured in milliseconds.

Latency describes the amount of time a delay takes. Absorption is a property in which signal can get lost by an undesired source absorbing the signal. Loss is a reduction in attenuation as it spreads through a space.

Question 10

Which word is used to describe the latency of traffic?

Answer 10

Delay is the amount of time it takes for a packet to travel from one point to the next measured in milliseconds. Variance in Delay is known as Jitter which is measured in Milliseconds.

Question 11

What does the absence of light typically mean on an interface status indicator?

Answer 11

When light isn’t present on a switchport’s LED status indicator, it typically means something in the physical layer isn’t up or functioning.

Question 12

You notice as you move farther from an access point, the signal strength and throughput capability weakens. What property are you likely experiencing?

Answer 12

Attenuation is a natural property that occurs as a reduction of signal when the distance from the source increases. This property applies to wireless signals from an AP, especially if not configured properly, or if there is something blocking the signal.

Question 13

You need to verify L3 host redundancy failover time after setting up a FHRP between 2 routers. You need to do this on a Windows host and need to continuously ping the virtual IP address, 192.168.1.1. Which of the following commands should you use?

Answer 13

ping -t 192.168.1.1

Question 14

Which Windows command line utility combines the functions of traceroute and ping?

Answer 14

PathPing is a windows utility that combines the functions of the ping command and tracert (traceroute) commands.

Question 15

Which command can you issue on a Windows workstation to display ARP information?

Answer 15

arp -a.

Question 16

Which of the following commands can be issued on a host to display its routing table?

Answer 16

The command route print is used to display a host’s routing table.

Question 17

Which of the following commands releases an assigned DHCP address on a Windows host?

Answer 17

the command ipconfig /release is used to immediately release an assigned DHCP address on a Windows host.

Question 18

You are troubleshooting connectivity issues on a network in a computer lab. You can’t seem to access websites on the internet, but you can ping an Internet web servers’ IP address. Which of the following is most likely causing the issue?

Answer 18

Given that you can ping a web server’s IP address, but not be able to perform name resolution is a good indicator that there is DNS (domain Name System) server issues.

Question 19

You have been tasked to move your organization’s IP addresses from static to DHCP assigned addresses. The only consideration is some hosts will still require static addressing. Later, you discover a host that got its IP address assigned by DHCP can’t communicate on the network. Which of the following could have caused this issue?

Answer 19

Given this situation, if a host received a duplicate address, it won’t be able to communicate in the network. The solution in this case would be to give up the leased address on the host and possibly look at addresses you could exclude on the DHCP server.