Network Troubleshooting and Tools (8) Flashcards
Which of the following protocols does the traceroute utility on Unix and Linux systems use to test TCP/IP connectivity?
ICMP
TCP
UDP
UDP
On Unix and Linux systems, the traceroute utility tests TCP/IP connectivity by transmitting User Datagram Protocol (UDP) messages. This is unlike the tracert utility on Windows systems, which uses Internet Control Message Protocol (ICMP) messages. Neither version uses TCP or HTTP
Alice is working on an older network with a Windows Internet Name Service (WINS) server, a Domain Name System (DNS) server, and an Internet router. A user is complaining that he suddenly can’t connect to hosts on other internal networks. The user isn’t having problems connecting to resources on his local network or the Internet. Alice asks the user whether anything is new or has been changed on the computer and discovers that he recently changed some Internet Protocol (IP) parameters. What should Alice do next?
Verify that the WINS server is up and running and properly configured.
Verify that the DNS server is up and running and properly configured.
Verify that the user’s IP configuration settings are correct.
Verify that the user’s IP configuration settings are correct.
Since only one user is reporting the problem, the user’s computer is the likeliest source of the problem. The user has probably changed or removed the WINS server address. If the user is working with an incorrect WINS address, he can access local network resources but not resources on another internal LAN. Also, he can access resources on the Internet, which means the Internet router and the DNS server are not the problem
Alice receives a call from a user who cannot connect to the company’s 802.11n wireless network with a laptop that has an 802.11g network adapter. Other users working in the same area are able to connect to the network without difficulty. Which of the following steps should Alice take first to try to resolve the problem? (Choose all correct answers.)
Change the channel used by the wireless access point.
Check whether the user is connecting to the correct SSID.
Check whether the wireless adapter in the user’s laptop is enabled.
Provide the user with an 802.11n wireless network adapter.
Check whether the user is connecting to the correct SSID.
Check whether the wireless adapter in the user’s laptop is enabled.
The first steps Alice should take are the simplest ones: make sure that the wireless interface in the user’s laptop is turned on and that she is attempting to connect to the correct SSID for the company network. Changing the channel would not be necessary unless other users in the area are also having problems due to interference. The 802.11n wireless networking standard is backward compatible with 802.11g, so it should not be necessary to provide the user with a new network adapter
Ralph has begun to receive calls from users reporting that they cannot access the local network or the Internet. Ralph checks their computers and discovers that all of the users with a problem have IP addresses in the 169.254.0.0/16 network, which is not the address used on Ralph’s network. Which of the following might be the cause of the problem?
The users have tried to modify their IP configuration settings.
There is a rogue DHCP server somewhere on the network.
The IP address leases assigned by the DHCP server have expired.
The IP address leases assigned by the DHCP server have expired.
The 169.254.0.0/16 network is used by Automatic Private IP Addressing (APIPA), a standard that provides DHCP clients with an IP address when they cannot contact a DHCP server. Unknown to Ralph, the DHCP server on his network has been down for over a week, and the users’ IP address leases have begun to expire. This causes them to revert to APIPA addresses. Multiple users changing their IP addresses would not result in them all using the same network address. A rogue DHCP would not be likely to deploy APIPA addresses to clients. Malware infections that modify IP addresses are rare
Ed has installed a separate 802.11n wireless network for guest users working in his company’s offices. The guest network is unsecured, and Ed has recently become aware that people outside the building are able to access it. Which of the following steps can Ed take to prevent users outside the building from accessing the guest network, while leaving it available to unauthenticated users inside the building? (Choose all correct answers.)
Move the wireless access point to the center of the building.
Lower the power level of the wireless access point.
Disable SSID broadcasting.
Implement MAC filtering.
Move the wireless access point to the center of the building.
Lower the power level of the wireless access point.
Disable SSID broadcasting.
Moving the access point to the center of the building will keep as much of its operational range inside the structure as possible. If the signals still reach outside the building, Ed can reduce the power level of the access point until the network is only accessible inside. Disabling SSID broadcasts will not defeat dedicated attackers, but it can prevent casual intruders from accessing the network. MAC filtering would require Ed to configure the access point with the MAC addresses of all devices that will access the network, which would be impractical in this case
Alice receives a call in which a user reports that he is unable to send print jobs to the network-attached workgroup printer near his desk. Which of the following tasks should Alice perform first?
Reinstall the printer driver on the user’s workstation.
Test network connectivity to the printer using the ping utility.
Examine the switches to which the user’s workstation and the printer are connected.
Test network connectivity to the printer using the ping utility.
The first phase of the troubleshooting process is gathering information. Learning whether the printer is accessible over the network can help Alice to isolate the location of the problem and develop a theory of probable cause. Installing drivers, checking switches, and upgrading firmware are all part of a later phase in the troubleshooting process: testing a theory to determine the cause of the problem
Alice receives a call from a user who cannot connect to the company’s 802.11g wireless network with a new laptop that has an 802.11ac network adapter. Other users working in the same area are able to connect to the network without difficulty. Which of the following steps can Alice perform to resolve the problem? (Choose all correct answers.)
Install an 802.11ac wireless access point on the network.
Change the channel used by the wireless access point.
Install an 802.11g wireless network adapter in the user’s laptop.
Move the user closer to the wireless access point.
Install an 802.11ac wireless access point on the network.
Install an 802.11g wireless network adapter in the user’s laptop.
The 802.11ac and 802.11g wireless networking standards are fundamentally incompatible. The 802.11g access point uses the 2.4 GHz band and the user’s 802.11ac laptop uses the 5 GHz band. Therefore, the only possible solutions are to install an 802.11ac access point or an 802.11g network adapter. Changing channels on the access point and moving the user will have no effect on the problem
Several accounting consultants are working in Ed’s office for the first time, and they are unable to connect to the 802.11g wireless network with their laptops. They are selecting the correct SSID from the Available Networks list, but they cannot connect, and there are no error messages of any kind. Which of the following tasks should Ed perform to try to resolve the problem?
Change the frequency used by the wireless access point from 2.4 GHz to 5 GHz.
Examine the area where the consultants are working for possible sources of signal interference.
Make sure that the consultants’ laptops are configured to use the correct wireless security protocol.
Make sure that the consultants’ laptops are configured to use the correct wireless security protocol.
The use of an incorrect wireless security protocol is a well-known source of errorless connection failures, so checking this will most likely enable Ed to locate the source of the problem. Channel overlap is a problem that Ed would check and resolve at the access point, not the users’ workstations. It is not possible to change the frequency on the access point because the 802.11g standard only supports the 2.4 GHz frequency. Although signal interference could conceivably be the cause for a connection failure, the users can see the network, so this is probably not the problem
Ralph has installed a new Category 5e cable run himself. He has attached keystone connectors to both ends of the cable, mounted the office-side connector to a wall plate, and mounted the datacenter connector into a patch panel. Then he took a patch cord and connected the patch panel port to an open port in one of the network switches. However, the LED on the switch port does not light. What should Ralph do?
Check the cable run for wiring faults.
Make sure the switch port is not disabled.
Plug a computer into the wall plate.
Plug a computer into the wall plate.
For the link pulse LED on the switch port to light up, there must be a completed connection between the switch and a computer at the other end. None of the other options will cause the LED to light
A user calls Ed at the help desk to report that his computer is displaying a Duplicate IP Address error message. This puzzles Ed because all of the network workstations should be configured to obtain their IP addresses from DHCP servers. Ed asks the user if he has changed the TCP/IP configuration settings on the computer recently. The user says no. Ed then asks of anybody else uses the workstation. The user says no. However, when Ed runs the ipconfig /all command on the user’s workstation, he sees that the DHCP Enabled setting reads No. What should Ed do next?
Accuse the user of changing the TCP/IP settings and then lying about it.
Activate the DHCP client on the workstation and close the trouble ticket.
Begin an investigation into the possibility of a rogue DHCP server on the network.
Activate the DHCP client on the workstation and close the trouble ticket.
Because Ed knows that the network workstations should be using DHCP to obtain their IP addresses, the best thing to do is to enable the DHCP client and close the ticket rather than configure the system with another static address. There is no indication that there is a rogue DHCP server on the network, since the workstation’s DHCP client is disabled. This is not the first time that Ed has had a user lie to him, nor will it be the last. He should just let it go and work on addressing the problem
Ralph is having trouble providing satisfactory wireless network performance to some executive offices at the far end of the building. The offices have heavy doors and insulated walls for sound dampening, and the occupants typically leave their doors closed during work hours. Which of the following types of radio signal interference is Ralph trying to overcome?
Reflection
Diffraction
Absorption
Absorption
Absorption is a type of interference that occurs when radio signals have to pass through barriers made of dense materials, such as walls and doors. In this case, the construction of the barriers has made them more formidable. Reflection is when signals bounce off of certain surfaces, such as metal. Refraction is when signals bend as they pass through certain barriers, such as glass or water. Diffraction is when signals have to pass around barriers to reach a particular destination. All of these phenomena can weaken the radio signals used in wireless networking, but absorption is the primary problem for Ralph in this case
Ralph is having trouble providing satisfactory wireless network performance to a row of glass-walled conference rooms at the far end of the building. The doors to the conference rooms are also made of glass and are always closed when meetings are in progress. Which of the following types of radio signal interference are likely to be the main issues that Ralph is trying to overcome? (Choose all correct answers.)
Reflection
Refraction
Diffraction
Attenuation
Refraction
Attenuation
Attenuation is the tendency of signals to weaken as they travel through a network medium. In the case of a wireless network, the medium is the air, and the farther away a wireless device is from the access point, the weaker the signal will be. Refraction is when signals bend as they pass through certain types of barriers, such as the glass walls of conference rooms. The bending changes the direction of the signals, possibly causing them to weaken in the process. Reflection is when signals bounce off of certain surfaces, such as metal. Diffraction is when signals have to pass around barriers to reach a particular destination. All of these phenomena can weaken the radio signals used in wireless networking, but attenuation and refraction are likely to be the primary problems for Ralph in this case
Ralph is having trouble providing satisfactory wireless network performance to some executive offices at the far end of the building. The wireless access point is based on the 802.11g standard. The offices have heavy doors and insulated walls for sound dampening, and the occupants typically leave their doors closed during work hours. Which of the following actions can Ralph take to provide the users in this offices with better wireless network performance?
Install an additional access point nearer to the offices.
Modify the access point to use higher number channels.
Upgrade the access point to a model based on the 802.11n standard.
Install an additional access point nearer to the offices.
The closer the users are to the access point, the stronger the signals will be. Installing an additional access point nearer to the executive offices will likely enable the signals to pass through the barriers more efficiently. The channel used by the access point, the standard on which the access point is based, and the broadcasting of SSID signals have no effect on the strength of the signals reaching the executive offices and will not resolve Ralph’s problem
Ralph’s company has expanded to include an additional building on the far end of the corporate campus, approximately four kilometers away from the building housing the datacenter. A single-mode fiber-optic cable connection has been installed between the new building and the datacenter for a 1000Base-BX10 connection, but the cable is not yet connected to a transceiver at the datacenter end. Noticing that there is a 1000Base-SX transceiver module in the datacenter store room, Ralph is wondering if he could use this on the new cable run. Which of the following are reasons why this might not work? (Choose all correct answers.)
Transceiver mismatch
Incorrect cable type
Excessive cable length
Wavelength mismatch
Transceiver mismatch
Incorrect cable type
Excessive cable length
Wavelength mismatch
The 1000Base-SX standard calls for multimode cable with a maximum length of approximately 500 meters, while the new cable run is 4,000 meters and uses single-mode cable. The 1000Base-SX transceiver will also be incompatible with the 1000Base-BX10 transceiver at the other end. 1000Base-BX10 uses wavelengths from 1,300 to 1,600 nanometers, whereas 1000Base-SX uses wavelengths of 770 to 860 nm
Ralph is working with an ADSL router that has a switch module containing four Ethernet ports, all of which are assigned to the default VLAN1. Ralph can plug a laptop into one of the router’s ports and access the Internet with no problems. Ralph now needs to connect the ADSL router to the company network so that the wireless access points on the network can provide users with Internet access through the ADSL router. However, when Ralph plugs the router into a network switch port in VLAN4, the switch starts generating “Native VLAN mismatch detected” errors every minute. Which of the following steps should be part of the solution Ralph implements to stop the error messages? (Choose all correct answers.)
Create a VLAN1 on the network switch.
Create a VLAN4 on the ADSL router’s switch module.
Configure the network switch port connected to the router to use VLAN1.
Configure the router port connected to the network switch to use VLAN4.
Create a VLAN4 on the ADSL router’s switch module.
Configure the router port connected to the network switch to use VLAN4.
The solution should call for Ralph to create a VLAN on the ADSL router that matches the VLAN the network switch port is using. Therefore, he should create a VLAN4 on the router and assign a port to it, which will be the port Ralph uses to connect the router to the network switch. There is no need to create a VLAN1 on the network switch, because all switches have a default VLAN called VLAN1. Modifying the VLAN assignments on the network switch is not a good idea, because it might interfere with the existing VLAN strategy in place
