Network Troubleshooting and Tools (6) Flashcards
Which of the following types of interference on a twisted pair network are designed to be prevented by the twists in the wire pairs inside the cable?
Crosstalk
EMI
Attenuation
Crosstalk
Crosstalk is a type of interference that occurs on copper-based networks when in a signal transmitted on one conductor bleeds over onto another nearby conductor. Twisted pair cables, which have eight or more conductors compressed together inside one sheath, are particularly susceptible to crosstalk. Twisting each of the separate wire pairs tends to reduce the amount of crosstalk to manageable levels. Twisting the wire pairs does not prevent signals from being affected by electromagnetic interference (EMI) or attenuation. Latency is a measurement of the time it takes for a signal to travel from its source to its destination
Which of the following indicators can you use to determine whether an adapter is connected to a functioning hub or switch?
Speed light-emitting diode (LED)
Collision LED
Link pulse LED
Link pulse LED
The link pulse LED indicates the adapter is connected to a functioning hub or switch. The speed LED specifies the data rate of the link. The collision LED lights up when collisions occur. There is no status LED on a network interface adapter
Ralph has been asked to create some new patch cables that will be used to connect patch panel ports to the network switches. He has been told that the patch panel connectors are all wired using the T568A pinout standard. Which of the following instructions should Ralph use when creating the patch cables?
Use T568A at both ends
Use T568A at one end and T568B at the other end
Use either standard, as long as both ends are the same
Use either standard, as long as both ends are the same
Either the T568A or the T568B pinout standard is acceptable. The patch cables will function properly as long as both ends are wired using the same pinout standard
Ed has discovered that, on some of his newly installed twisted pair cable runs, the installer has stripped away nearly a foot of the cable sheath at each end and has untwisted the wire pairs before attaching them to the connectors. Which of the following problems is the network more likely to experience due to the untwisted wires?
Jitter
Attenuation
Crosstalk
Crosstalk
Crosstalk is a type of interference that occurs on copper-based networks when in a signal transmitted on one conductor bleeds over onto another nearby conductor. Twisted pair cables, which have eight or more conductors compressed together inside one sheath, are particularly susceptible to crosstalk. Twisting each of the separate wire pairs tends to reduce the amount of crosstalk to manageable levels. Untwisting the pairs leaves them more susceptible to crosstalk. Jitter, attenuation, and electromagnetic interference (EMI) are all conditions that can affect the performance of a wired network, but they are not directly related to untwisted wire pairs
Ed is experiencing bad network performance on some new twisted pair cable runs that he recently had installed. After ruling out all other causes, he tests the cables with a tone generator and locator and finds no faults. Finally, he examines the cable connectors more closely and finds that, while the pins at one end of the cable are correctly connected to their corresponding pins at the other end, in some cases there are two solid color wires twisted together in a pair. Which of the following types of faults has Ed discovered?
Open circuit
Short circuit
Split pairs
Split pairs
A split pair is a connection in which two wires are incorrectly mapped in exactly the same way on both ends of the cable. Each pin on one end of the cable is correctly wired to the corresponding pin at the other end, but the wires inside the cable used to make the connections are incorrect. In a properly wired connection, each twisted pair should contain a colored signal wire and a striped ground wire. In a split pair, you can have two signal wires twisted together as a pair. This can generate excessive amounts of crosstalk, corrupting both of the signals involved. Because all of the pins are connected properly, a tone generator and locator cannot detect this fault. An open circuit would manifest as a failure to detect a tone on a wire, indicating that there is either a break in the wire somewhere inside the cable or a bad connection with the pin in one or both connectors. A short is when a wire is connected to two or more pins at one end of the cable or when the conductors of two or more wires are touching inside the cable. Having transposed pairs is a fault in which both of the wires in a pair are connected to the wrong pins at one end of the cable. All three of these faults are detectable with a tone generator and locator
Ed is examining some twisted pair cable runs that were recently installed in his office by an outside contractor. Looking at the connectors, he sees a variety of pinout combinations. Which of the following pinouts must Ed have rewired because they are incorrect? (Choose all correct answers.)
White/orange, orange, white/green, blue, white/blue, green, white/brown, brown
White/green, green, white/orange, blue, white/blue, orange, white/brown, brown
White/orange, orange, white/green, green, white/blue, blue, white/brown, brown
White/brown, white/green, white/orange, blue, white/blue, orange, green, brown
White/orange, orange, white/green, green, white/blue, blue, white/brown, brown
White/brown, white/green, white/orange, blue, white/blue, orange, green, brown
Option A is the T568B pinout, and option B is the T568A pinout. Both of these are correct and may be used. Options C and D are both incorrect and can result in excessive amounts of crosstalk
Ed is the administrator of his small company’s network. A user calls the help desk and reports that she can’t connect to the network. She has never had any problems connecting before now, and she says that nothing on her computer has changed. Ed goes to the user’s location to investigate and notices that the link pulse light-emitting diode (LED) on the switch port for the user’s computer is not lit. What should Ed do next to isolate and fix the problem? (Choose all correct answers.)
Verify that the cable is securely connected to the switch.
Verify the patch cable is pinned and paired properly.
Replace the existing patch cable with a straight-through cable that is known to be good.
Replace the existing patch cable with a crossover cable that is known to be good.
Verify that the cable is securely connected to the switch.
Replace the existing patch cable with a straight-through cable that is known to be good.
In this scenario, the user was previously able to connect to the network. There have been no hardware or software changes to the computer. These factors indicate that there is possibly a physical layer problem, such as a loose cable, a faulty cable, a bad switch port, or a bad network interface adapter in the computer. Since the user’s cable previously worked, there is no need to verify that it is pinned and paired properly, and crossover cables are not used to connect workstations to switches. The first thing Ed should do is verify that all cable connections are secure. If he finds a loose cable and the link pulse LED lights up when he reseats it, then the cable was the problem. If the link pulse LED does not light, Ed should replace the existing cable with a straight-through cable that is known to be good. If the LED lights up, the existing cable was probably faulty. If the LED does not light up, Ed should suspect a faulty network interface adapter or switch port, and try moving the cable to a port on the switch that is known to function. If the connection works, the problem is probably a failed switch port. If the connection still does not work, then the fault is probably the network interface adapter in the user’s computer
Ralph has been asked to create some new patch cables that will be used to connect patch panel ports to the network switches. He has been told to use the T568B pinout standard for all of the cable connectors. Ralph gathers the materials and the tools needed to complete the task, but he is not sure about the T568B pinout. Which of the following pinouts must Ralph use when creating the patch cables?
White/orange, orange, white/green, blue, white/blue, green, white/brown, brown
White/green, green, white/orange, blue, white/blue, orange, white/brown, brown
White/orange, orange, white/green, green, white/blue, blue, white/brown, brown
White/orange, orange, white/green, blue, white/blue, green, white/brown, brown
Option A is the T568B pinout that Ralph should use when attaching connectors to the cables. Option B is the T568A pinout, which would also work but that Ralph has been instructed not to use. Options C and D are both incorrect and can result in excessive amounts of crosstalk
Ralph is setting up a wireless network using the 2.4 GHz band. Which of the following channels should he use to avoid channel overlap? (Choose all correct answers.)
1
4
6
8
11
1
6
11
The 2.4 GHz band used by wireless LANs (WLANs) consists of channels that are 20 (or 22) MHz wide. However, the channels are only 5 MHz apart, so there is channel overlap that can result in interference. Channels 1, 6, and 11 are the only channels that are far enough apart from each other to avoid any overlap with the adjacent channels. Channels 4 and 8 are susceptible to overlap
Ralph is adding new workstations to his wireless network, which uses an access point that is configured to use WPA2 encryption. However, after configuring the wireless network adapter on the first workstation, Ralph finds that it is not connecting to the network. The access point is listed on the Available Networks display, and there are no error messages or indications of a problem, just a failure to connect. Which of the following is most likely to be the problem?
Incorrect passphrase
Channel overlap
Incorrect SSID
Incorrect passphrase
Specifying the wrong passphrase for the encryption protocol is the most common cause of a failure to connect to the network with no indication of an error. Channel overlap or a poor signal-to-noise ratio, caused by a microwave oven or other device, could result in a weak signal, either of which would be indicated in the list of available networks. Incorrect SSID is not likely to be the error, as long as Ralph selected the access point from the list
Ralph is adding new workstations to his wireless network, which uses an access point that is configured to use WPA2 encryption. However, after installing the wireless network adapter on the first workstation, Ralph finds that he cannot see the wireless access point on the Available Networks display. Which of the following could be the problem? (Choose all correct answers.)
Incorrect passphrase
Channel overlap
Incorrect SSID
Incorrect antenna placement
Channel overlap
Incorrect antenna placement
Both interference resulting from channel overlap and incorrect antenna placement could render the workstation unable to make contact with the access point. An incorrect passphrase would not be the problem unless Ralph had already seen the access point and attempted to connect to it. An incorrect SSID would be the problem only if Ralph had already attempted to manually enter an SSID
Ralph is the administrator of a small company’s wireless network. He has recently discovered evidence that users outside of the company’s office space have been accessing its wireless network. The office is located in a narrow space against the building’s outside wall. Ralph is concerned that the network’s wireless access point is extending coverage outside the building. Speaking with a consultant friend of his, Ralph is advised to install a different type of antenna on his access point. Which of the following antenna types would most likely help Ralph to alleviate the problem?
Dipole
Yagi
Patch
Patch
A patch antenna is a flat device that transmits signals in a half-spherical pattern. By placing the antenna against the building’s outer wall, Ralph can provide coverage inside the building and minimize coverage extending to the outside. A dipole antenna is another name for the omnidirectional antenna usually provided with an access point. A unidirectional antenna directs signals in a straight line, which would not provide the coverage Ralph needs. A Yagi antenna is a type of unidirectional antenna
Trixie has recently moved to a new office in her company’s building, down the hall from her old one. Since the move, she has only been able to access the wireless network with her laptop intermittently. She never had a problem in her previous location. Which of the following could possibly be the cause of her problem? (Choose all correct answers.)
Trixie’s new office is farther from the access point than her old one.
Her laptop is connecting to the wrong SSID.
The access point is using an omnidirectional antenna.
There are too many walls between Trixie’s new office and the access point.
Trixie’s new office is farther from the access point than her old one.
There are too many walls between Trixie’s new office and the access point.
Greater distance from the access point or interference from intervening walls can both cause a weakening of wireless signals, resulting in the intermittent connectivity that Trixie is experiencing. An incorrect SSID would prevent Trixie’s laptop from ever connecting to the network. An omnidirectional antenna generates signals in every direction, which would not account for Trixie’s problem
Alice is a new hire at Adatum Corp., and when she asks about wireless network access for her laptop, she is given an SSID and a WPA2 passphrase. Later, in the lunchroom when she tries to connect her laptop to the network, she cannot see the SSID she was given in the available networks list, although she can see other networks. What should Alice do next to try to resolve the problem?
Type in the WPA2 passphrase.
Type the SSID in manually.
Move closer to the wireless access point.
Type the SSID in manually.
It is possible that the wireless access point has been configured not to broadcast the network’s SSID as a security measure, so Alice should first attempt to access it by typing the SSID in manually. She would not be able to type in the WPA2 passphrase until she is connecting to the SSID. Moving the laptop closer to the access point or away from possible sources of electromagnetic interference might be solutions to the problem, but they should not be the first thing Alice tries
Alice is a new hire at Adatum Corp., and when she asks about wireless network access for her laptop, she is given an SSID and a passphrase. She is also told that she must add the SSID manually. Later, she types in the SSID she was given, and the computer prompts her to select a security type. Not knowing which option to choose, she selects 802.1x, because it sounds as though it should be the most secure. However, this option does not enable her to enter her passphrase, so she selects another option, WEP, and is able to type in the passphrase. However, her laptop says she “Can’t connect to this network.” Which of the following is the most likely cause of Alice’s problem?
Overcapacity
Frequency mismatch
Security type mismatch
Security type mismatch
The most likely cause of Alice’s problem is that she has selected an incorrect security type. Wired Equivalent Privacy (WEP) is still provided as an option on many wireless devices, but it has long since been found to be insecure and is almost never used. Alice should try selecting the other security types that enable her to enter her passphrase, such as Wi-Fi Protected Access II (WPA2). Although the other options are possible causes of the problem, security type mismatch is the most likely cause
