5.2 Given a scenario, troubleshoot common cable connectivity issues and select the appropriate tools.
Ralph wants to use Power over Ethernet (PoE) to supply power to security cameras located throughout his company's datacenter. The Ethernet network is currently running at Gigabit Ethernet speed, but Ralph is planning to downgrade the camera connections to 100Base-TX, because that standard has two wire pairs free for the transmission of power. Which of the following statements about Ralph's plan is true? a) Ralph's planning is correct; only 10Base-T and 100Base-TX support PoE. b) Ralph's plan will not work because 100Base-TX is not compatible with PoE. c) Ralph's plan will work, but it is not necessary to downgrade the connections to 100Base-TX. d) Ralph's plan will not work, because PoE cannot supply enough power for the cameras.
C. The Alternative B PoE variant can use the spare wire pairs in a Category 5 (Cat 5) or better 10Base-T or 100Base-TX cable to supply power to connected devices. The Alternative A and 4PPoE variants cannot use the spare wire pair in this manner; they supply power using the wire pairs that carry data at the same time. For Gigabit Ethernet or faster installations, Alternative B is capable of using the data wire pairs.
Ralph's company has expanded to include an additional building on the far end of the corporate campus, approximately 4 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 storeroom, 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 that apply.) a) Transceiver mismatch b) Incorrect cable type c) Excessive cable length d) Wavelength mismatch
A, B, C, D. 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 (nm), whereas 1000Base-SX uses wavelengths of 770 to 860 nm.
Which of the following should a troubleshooter look for when a duplex mismatch is suspected on an Ethernet network? (Choose all that apply.) a) Collisions b) Runt frames c) CRC errors d) Failed ping tests
A, B, C. There should be no collisions at all on a full-duplex network, so collisions indicate that at least one side of the connection is trying to operate in half-duplex mode. Ethernet running over twisted-pair cable, in its original half-duplex mode, detects collisions by looking for data on the transmit and receive pins at the same time. In full-duplex mode, data is supposed to be transmitted and received at the same time. In a duplex mismatch, in which one side of a connection is configured to use full duplex and the other end is configured to use half duplex, the full-duplex communications originating from one side look like collisions to the half-duplex side. The half-duplex adapter transmits a jam signal as a result of each collision, which causes the full-duplex side to receive an incomplete or damaged frame, which are perceived as runts or through Cyclic Redundancy Check (CRC) errors. Both sides then start to retransmit frames in a continuing cycle, causing network performance to diminish. Ping tests do not detect a duplex mismatch, because `ping` only transmits a small amount of data in one direction at a time. The mismatch only becomes apparent when the systems transmit large amounts of data.
Which of the following application layer protocols includes a program that enables a user to log on to a network device and execute commands on the remote system using a command-line interface? (Choose all that apply.) a) Telnet b) File Transfer Protocol (FTP) c) Simple Network Management Protocol (SNMP) d) Domain Name System (DNS) e) Nslookup
A, B. Both Telnet and FTP are protocols that include command-line client applications, with Telnet providing terminal emulation and FTP file transfer functionality. SNMP and DNS are both application layer protocols, but neither one includes a program. Nslookup has a command-line interface, but it executes commands on the local system, not a remote one.
Ed is trying to troubleshoot a problem that has caused a wired network connection to slow down noticeably. Which of the following wired network problems will cause a drastic slowdown of a network connection, without causing it to fail completely? (Choose all that apply.) a) Bottleneck b) Speed mismatch c) Duplex mismatch d) TX/RX reversal
A, C. A bottleneck is a component involved in a network connection that is not functioning correctly, causing a traffic slowdown that affects the entire network. A duplex mismatch occurs when one side of a connection is configured to use full duplex and the other end is configured to use half duplex. When this occurs, the full-duplex communications on the one side look like collisions to the half-duplex side. The half-duplex adapter transmits a jam signal as a result of each collision, which causes the full-duplex side to receive an incomplete frame. Both sides then start to retransmit frames in a continuing cycle, causing network performance to diminish drastically. A speed mismatch or a Transmit and Receive (TX/RX) reversal will stop network communication completely.
Which of the following statements about cable certifiers are true? (Choose all that apply.) a) A cable certifier eliminates the need for tools like tone generators and wiremap testers. b) Cable certifiers are the most inexpensive cable testing solution. c) Cable certifiers must be reconfigured whenever a new cable specification is standardized. d) Cable certifiers can only test copper-based cables.
A, C. Cable certifiers can detect all of the faults that tone generators and wiremap testers can detect, and they can do a great deal more, such as specify whether a cable run meets the performance specifications defined in a cable standard. When testing a new cable type, the specifications defined in the cable standard must be added to the device. Cable certifiers are far more expensive than most other cable testing solutions. Cable certifiers are available that support various cable media, including copper and fiber optic.
Which of the following Windows command-line utilities produced the output shown here? a) ``` b) Reply from 97.74.144.153: bytes=32 time=111ms TTL=53 c) ``` 1. `ping` 2. `tracert` 3. `netstat` 4. `arp` 5. `hostname`
A. The Windows `ping` utility functions by transmitting a series of Internet Control Message Protocol (ICMP) Echo Request messages to a specified destination. The destination system responds with ICMP Echo Reply messages that are listed in the output display. The `tracert`, `netstat`, `arp`, and `hostname` utilities are not capable of producing this output.
Ralph is testing a twisted-pair cable run using a tone generator and locator. When he applies the tone generator to one particular wire at one end of the cable, he fails to detect a tone at the other end. Which of the following faults has Ralph discovered? a) Open b) Short c) Split pair d) Crosstalk
A. The failure to detect a tone on a wire indicates 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. This condition is called an open circuit. A short is when a wire is connected to two or more pins at one end of the cable. A split pair is a connection in which two wires are incorrectly mapped in exactly the same way on both ends of the cable. Crosstalk is a type of interference caused by signals on one wire bleeding over to other wires.
Alice has recently installed some new computers onto her Gigabit Ethernet network. To ensure the best possible network performance, she has configured the network adapters in the new computers to run at 1 Gbps speed and use full-duplex communication. Once the computers are in service, however, Alice begins getting reports of extremely poor network performance on those machines. She tries running some ping tests and does not see any problem. She calls in a consultant to perform a packet analysis, and the consultant detects large numbers of packet collisions, late collisions, Cyclic Redundancy Check (CRC) errors, and runt frames. Which of the following could conceivably be the problem? a) Duplex mismatch b) TX/RX reversal c) Incorrect cable type d) Damaged cables
A. There should be no collisions on a full-duplex network, so the problem is clearly related to the duplexing of the communications. Ethernet running over twisted-pair cable, in its original half-duplex mode, detects collisions by looking for data on the Transmit and Receive (TX/RX) pins at the same time. In full-duplex mode, data is supposed to be transmitted and received at the same time. When one side of a connection is configured to use full duplex, as Alice's new computers are, and the other end is configured to use half duplex (as the switches must be), the full-duplex communications on the one side look like collisions to the half-duplex side. The half-duplex adapter transmits a jam signal as a result of each collision, which causes the full-duplex side to receive an incomplete frame. Both sides then start to retransmit frames in a continuing cycle, causing network performance to diminish drastically. The ping tests do not detect a problem, because `ping` only transmits a small amount of data in one direction at a time. The other options would likely cause the ping tests to fail as well. The solution to the problem is to configure all of the devices to autonegotiate their speed and duplex modes.
Ralph has to spend the day completing a twisted-pair cable installation in his office. Contractors have already pulled the cables through the walls and ceilings. Ralph only has to attach connectors to the ends of the cables, both internal cable runs and patch cables. Which of the following tools will Ralph need? (Choose all that apply.) a) Telepole b) Crimper c) Punchdown tool d) Pigtail splicer
B, C. A crimper is a plier-like tool that cable installers use to attach RJ45 connectors to patch cables. A punchdown tool is a tool that cable installers use to attach keystone connectors to cable ends, for use in wall plates and patch panels. A telepole is a device used to run cables through walls, floors, and ceilings, but since the cable runs have already been pulled, Ralph will not need this tool. A pigtail splicer is a tool used only in fiber-optic cable installations.
After experiencing some problems with devices connected to the company's fiber-optic network, Alice brings in a contractor to test the fiber-optic cable runs. The contractor detects a significant amount of decibel (dB) loss in some of the cable runs, which could be the source of the problems. Which of the following are possible causes of the decibel loss? (Choose all that apply.) a) Electromagnetic interference b) Dirty optical cables c) Excessive cable length d) Signal crosstalk
B, C. Dirt on fiber-optic cable connectors can reduce the strength of the signal, resulting in decibel loss. Excessive cable length can result in greater attenuation and weaker signals due to the decibel loss. Electromagnetic interference and signal crosstalk are both factors that can affect copper cable transmissions, but not fiber optic.
Ed is trying to troubleshoot a problem with his wired network, and his research has led him to a list of possible network faults. The list is rather old, however, and Ed is wondering if some of the problems are relevant. Which of the following wired network problems no longer occur with modern Gigabit Ethernet switches and network adapters in their default configurations? (Choose all that apply.) a) Bottleneck b) Speed mismatch c) Duplex mismatch) d) Transmit and Receive (TX/RX reversal
B, C. The Gigabit Ethernet standards call for switches and network adapters to support autonegotiation by default, which enables devices to communicate and select the best network speed and duplex mode available to them both. Therefore, speed mismatches and duplex mismatches no longer occur unless someone modifies the speed or duplex settings to incompatible values on one or both devices.
Ed is trying to troubleshoot a problem that has caused a wired network connection to fail completely. Which of the following wired network problems will cause a complete failure of a network connection? (Choose all that apply.) a) Bottleneck b) Speed mismatch c) Duplex mismatch d) TX/RX reversal e) Bad switch port
B, D, E. A speed mismatch on a wired network only occurs when two devices are configured to use a specific transmission speed and those speeds are different. In that case, network communication stops. For network communication to occur on a twisted-pair network, transmit (TX) pins must be connected to receive (RX) pins. If the connections are reversed, no communication occurs. If the switch port to which a computer is connected is bad, there will be no network communication. Bottlenecks and duplex mismatches will slow down network communications, but they will not stop them completely.
Which of the following tools can you use to create your own twisted pair patch cables? (Choose all that apply.) a) Punchdown tool b) Crimper c) Pliers d) Wire stripper
B, D. A crimper is a device used for attaching connectors to patch cables. A wire stripper, while not essential to the process, can simplify the task of preparing the cable. A punchdown tool is used for attaching keystone connectors to cable ends, for use in wall plates and patch panels. A standard set of pliers is not used in the process of attaching connectors.
Ralph is attempting to access a Domain Name System (DNS) server located on the other side of a router, but his attempt fails with an error stating that the destination port UDP 53 is unreachable. His first step in troubleshooting the problem is to try using the `nslookup` utility to access that specific DNS server. This too fails. Next, he uses the `ping` utility with the DNS server's Internet Protocol (IP) address. The ping test is successful, indicating that the server is up and running. Which of the following are possible causes of the problem? (Choose all that apply.) a) The router connecting the networks is not running DNS and will not forward this type of datagram. b) The DNS process on the remote server is not running. c) The TCP/IP host configuration on your computer is improperly configured. d) The TCP/IP host configuration on the DNS server computer is improperly configured. e) There is a firewall blocking the DNS server's UTP 53 port.
B, E. One possible cause of the problem is that the DNS process on the remote server is corrupted or not running. Another possible cause is that there is a firewall blocking access to the server's Unshielded Twisted Pair (UTP) port 53. Both of these would render the port unreachable. The Transmission Control Protocol/Internet Protocol (TCP/IP) client on the server is operating, as verified by the `ping` utility. This means that the IP host configurations on Ralph's computer and on the DNS server are both functioning. The router does not need to be running DNS to forward datagrams.
Which of the following utilities can you use to view resource record information on a particular Domain Name System (DNS) server? (Choose all that apply.) a) `netstat` b) `nslookup` c) `nbtstat` d) `arp` e) `dig`
B, E. `nslookup` and `dig` are both command-line utilities that you can direct to a specific DNS server and then generate queries that display resource record information the program retrieves from the server. `netstat` displays information about networking protocols, whereas `nbtstat` displays information derived from the system's Network Basic Input/Output System (NetBIOS) over Transmission Control Protocol/Internet Protocol (TCP/IP) implementation. `arp` is a tool that you can use to display and manage a system's Address Resolution Protocol (ARP) table entries. `netstat`, `nbtstat`, and `arp` are not able to display resource record information.
Ralph is testing a twisted-pair cable run using a tone generator and locator. When he applies the tone generator to a particular pin at one end of the cable, he detects a tone on two pins at the other end. Which of the following faults has Ralph discovered? a) Open b) Short c) Split pair d) Crosstalk
B. 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. This would cause a tone applied to a single pin at one end to be heard on multiple pins at the other end. 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 split pair is a connection in which two wires are incorrectly mapped in exactly the same way on both ends of the cable. Crosstalk is a type of interference caused by signals on one wire bleeding over to other wires.
Ralph's company has engaged a firm of wiring contractors to install some new fiber-optic cable runs. Before the cables are connected to any devices, Ralph wants to confirm that they have been installed to proper specifications. He brings in a contractor from another firm to test the cable runs. To test each cable run, the contractor connects a light source to one end of the cable and a measuring device to the other end. Which of the following is the correct name for this testing device? a) Optical power meter b) OLTS c) OTDR d) Multimeter
B. An optical loss test set (OLTS) is the term for the combination of an optical light source and an optical power meter. The optical power meter by itself cannot be used to test the cable runs when there are no devices connected to them. An Optical Time Domain Reflectometer (OTDR) is a device for measuring the lengths and other characteristics of fiber-optic cables. A multimeter is a device for measuring the electric current on a copper cable.
Ed has discovered that some of the twisted-pair cable runs on his newly installed Ethernet network are well over 100 meters long. Which of the following problems is his network likely to experience due to cable segments that are greater than the specified length? a) Jitter b) Attenuation c) Crosstalk d) EMI
B. Attenuation is the weakening of a signal as it travels long distances, whether on a wired or wireless medium. The longer the transmission distance, the more the signal weakens. Cable length specifications are designed in part to prevent signals from attenuating to the point at which they are unviable. Jitter, crosstalk, and electromagnetic interference (EMI) are all conditions that can affect the performance of a wired network, but they are not directly related to the length of the cable.
Which of the following cable installation tools is likely to be the most expensive? a) A crimper b) A cable certifier c) A punchdown tool d) A wiremap tester
B. Crimpers and punchdown tools are relatively simple and inexpensive mechanical devices that cable installers use to connect bulk cable to connectors. A wiremap tester is an electronic device for cable testing, but it is still relatively simple. A cable certifier is a complex electronic device that can perform a battery of tests on a cable run, confirm that the cable conforms to the required wiring standards, and maintain records of the testing procedure. Cable certifiers are by far the most expensive of the devices listed.
Users are having trouble connecting to Internet hosts. Alice suspects that there is a problem with the Domain Name System (DNS) server, and she wants to verify this. Which of the following steps can she take to determine whether the DNS server is resolving Internet hostnames? a) Issue the `ipconfig` command from a local workstation b) Try to connect to a host using the IP address instead of the hostname c) Ping the DNS server to see if it is functioning d) Use the `tracert` command to test the functionality of the DNS server
B. If Alice suspects that a DNS server is not resolving hostnames, she should try connecting to a remote host using the Internet Protocol (IP) address instead of the name. If she can connect, she knows that all internal Local Area Network (LAN) components and the Internet gateway are functioning, and the remote host is functioning. The problem most likely lies within the DNS server itself. If Alice cannot connect to a remote host using the IP address, the problem is not the DNS server. She would need to do more testing to isolate the problem device and the affected area. `ipconfig` is a workstation command that enables you to verify the local IP configuration; it is not used to test a DNS server's functionality. Using the `ping` command will only tell you whether the computer hosting the DNS service is functioning at the network layer of the Open Systems Interconnection (OSI) model; it will not test the DNS service functionality. The `tracert` (or `traceroute` ) command is used to identify the hop-by-hop path taken to reach a destination; it does not allow you to test functionality above the network layer of the OSI model.
Which of the following command-line utilities is capable of performing the same basic function as `traceroute` or `tracert`? a) `ping` b) `pathping` c) `netstat` d) `route`
B. Like `traceroute` and `tracert`, `pathping` is capable of generating a list of the routers that packets pass through on the way to a specific destination system. `pathping` also displays the percentage of lost packets for each hop, which `traceroute` and `tracert` cannot do. The `ping`, `netstat`, and `route` utilities are not capable of displaying route traces.
Ralph is working on a new twisted-pair network cable installation on which the individual cable runs were not properly labeled as they were pulled. Ralph now has to trace each of the cable ends in the office area to the correct cable end in the data center and label them correctly. Which of the following tools should Ralph use to locate the correct cable in a bundle of unlabeled cable ends? a) Cable certifier b) Tone generator and locator c) OTDR d) Multimeter
B. Ralph can use a tone generator and locator to locate the correct cable associated with each office connection. By connecting the tone generator to one end of a cable run, he can use the locator to find the other end. A cable certifier identifies a variety of cable performance characteristics, typically including cabling length, signal attenuation, and crosstalk. An Optical Time Domain Reflectometer (OTDR) is a device for measuring the lengths and other characteristics of fiber-optic cables. A multimeter is a device for measuring the electric current on a copper cable.
Which of the following Windows command-line utilities produced the output shown here? a) ``` b) 1 <1 ms <1 ms <1 ms RT-N86U [192.168.2.99] c) ``` 1. `ping` 2. `tracert` 3. `netstat` 4. `arp` 5. `hostname`
B. The Windows `tracert` utility functions by transmitting a series of Internet Control Message Protocol (ICMP) Echo Request messages to a specified destination with incrementing Time to Live (TTL) values. Each successive message reaches one hop farther on the route to the destination before timing out. The `tracert` display therefore lists the names and addresses of the routers that packets must traverse to reach the destination. The `ping`, `netstat`, `arp`, and `hostname` utilities are not capable of producing this output.
Ralph is testing some newly installed twisted-pair cable runs on his network using a wiremap tester, and he has found one run that appears to have a cable break. However, the connectors at both ends are correctly installed, so the break must be somewhere inside the cable itself, which is nearly 100 meters long. Which of the following tools can Ralph use to determine the location of the cable break? (Choose all that apply.) a) Tone generator and locator b) Multimeter c) Time-domain reflectometer d) Cable certifier
C, D. A time-domain reflectometer (TDR) is a device that determines the length of a cable by transmitting a signal at one end and measuring how long it takes for a reflection of the signal to return from the other end. Using this information and the cable's nominal velocity of propagation (NVP)—a specification supplied by the cable manufacturer—the device can calculate the length of a cable run. In a cable with a break in its length, a TDR calculates the length of the cable up to the break. Cable certifiers typically have time-domain reflectometry capabilities integrated into the unit. A tone generator and locator or a multimeter cannot locate a cable break.
Alice is the network administrator of her company's network. The company has just moved into a building that has existing Category 6 (Cat 6) Unshielded Twisted Pair (UTP) cabling. However, none of the cable connections have been labeled, and Alice is trying to identify and document where each cable run starts and ends. Which tools can Alice use for this purpose? (Choose all that apply.) a) A packet sniffer b) A loopback adapter c) A tone generator and locator d) A wiremap tester
C, D. Alice can use a tone generator and locator or a wiremap tester to identify and test cable connections. By connecting the tone generator or the remote wiremap unit to one end of a cable run, she can use the locator or the master wiremap unit to find the other end. This can enable her to identify a starting point and an ending point for a cable run. A loopback adapter is used to test the transmission and reception capabilities of a port. A packet sniffer captures and analyzes network traffic; it cannot identify cables.
Ralph is using a tone generator and locator to test some newly installed twisted-pair cable runs on his network. Which of the following cable faults will he be unable to detect? a) Open b) Short c) Split pair d) Transposed pairs
C. 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 signal wire and a ground wire. In a split pair, it is possible to 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. 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.
Which of the following cable faults increases a twisted-pair cable's susceptibility to crosstalk? a) Open b) Short c) Split pair d) Transposed pairs
C. 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 signal wire and a ground wire. In a split pair, it is possible to have two signal wires twisted together as a pair. This can generate excessive amounts of crosstalk, corrupting both of the signals involved. Open circuits, shorts, and transposed pairs interfere with cable performance but do not make it more susceptible to crosstalk.
Ed is experiencing poor network performance on some new twisted-pair cable runs. 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? a) Open circuit b) Short circuit c) Split pairs d) Transposed wires
C. A split pair is a connection in which two wires are incorrectly mapped in exactly the same way on both ends of the cable. In a properly wired connection, each twisted pair should contain a colored signal wire and a striped ground wire. In a split pair, it is possible to 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 or a bad connection in one or both connectors. A short is when a wire is connected to two or more pins or when the conductors of two or more wires are touching. 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.
Which of the following terms describes the progressive weakening of transmitted signals as they travel along a network medium? a) Absorption b) Latency c) Attenuation d) Crosstalk
C. Attenuation is the weakening of a signal as it travels long distances, whether on a wired or wireless medium. The longer the transmission distance, the more the signal weakens. Absorption is the tendency of a wireless signal to change as it passes through different materials. Latency is a measurement of the time it takes for a signal to travel from its source to its destination. Crosstalk is a type of interference that occurs on wired networks when a signal bleeds over to an adjacent wire.
Delays in the transmission of data packets over a network can result in temporary service interruptions, dropouts, or even data loss. Which of the following terms is used to describe these delays? a) Crosstalk b) Electromagnetic interference (EMI) c) Jitter d) Attenuation
C. Jitter is defined as delays in the transmission of individual network packets. For audio or video transmissions, jitter can result in dropped words or frames. For data file transmissions, jitter can require retransmission of packets.
Alice's company has moved to a building that was prewired for twisted-pair Ethernet. However, since installing the company's Gigabit Ethernet equipment using the existing cable runs, performance has been poor. After performing some packet captures and analyzing the traffic samples, Alice discovers that there are a great many Ethernet frames being retransmitted. Next, she examines the cable runs in the drop ceilings. They do not appear to be overly long, and they do not appear to run near any major sources of electromagnetic interference. Which of the following could be the problem? a) Some of the cable runs are using T568A pinouts and some are using T568B. b) The cables only have two wire pairs connected, instead of four. c) The existing cable is not rated for use with Gigabit Ethernet. d) There are mismatched transceivers at the cable ends.
C. Of the options provided, the only possible source of the problem is that the cable runs are using a cable type not rated for Gigabit Ethernet. Some older buildings might still have Category 3 cable installed, which was used in the original twisted-pair Ethernet specification. Cat 3 is unsuitable for use with Gigabit Ethernet in many ways and can result in the poor performance that Alice is experiencing. A cable installation with runs wired using different pinout standards will not affect performance as long as each run uses the same pinouts at both ends. Gigabit Ethernet will not function at all if only two wire pairs are connected. The transceivers are located in the equipment that Alice's company brought from the old location, so they are not mismatched.
Which of the following Windows command-line utilities produced the output shown here? a) ``` b) Active Connections c) ``` 1. `ping` 2. `tracert` 3. `netstat` 4. `arp` 5. `hostname`
C. Running the Windows `netstat` utility with no parameters generates a list of the workstation's active connections. The `ping`, `tracert`, `arp`, and `hostname` utilities are not capable of producing this output.
Which TCP/IP utility should you use to most easily identify a malfunctioning router on your network? a) `ifconfig` b) `ping` c) `traceroute` d) `netstat`
C. The `traceroute` (or `tracert` ) utility can locate a malfunctioning router by using an Echo Request messages with incrementing Time to Live (TTL) values. `ifconfig` is a network configuration utility for Unix and Linux systems; `ping` can test connectivity to another Transmission Control Protocol/Internet Protocol (TCP/IP) system, but it cannot locate a malfunctioning router; and `netstat` displays information about network connections and traffic but cannot locate a malfunctioning router.
Which of the following indicators can you use to determine whether an adapter is connected to a functioning hub or switch? a) Speed Light-Emitting Diode (LED) b) Collision LED c) Link pulse LED d) Status LED
C. 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.
Alice has been told by a consultant that the newly installed twisted-pair cable runs on her network might have split pairs. Which of the following cable testing tools can she use to detect split pairs? a) Tone generator and locator b) Wiremap tester c) Multimeter d) Cable certifier
D. 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 signal wire and a ground wire. In a split pair, it is possible to 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, and neither can a wiremap tester or a multimeter. However, a cable certifier is a highly sophisticated electronic device that can detect all types of cable faults, including split pairs, as well as measure cable performance characteristics.
Ed has discovered that some of the twisted-pair cables on his newly installed network are running right alongside fluorescent light fixtures in the drop ceiling. Which of the following problems is the network likely to experience due to the cables' proximity to the fixtures? a) Jitter b) Attenuation c) Crosstalk d) EMI
D. Fluorescent light fixtures and other devices in an office environment can generate magnetic fields, resulting in electromagnetic interference (EMI). When a copper-based cable runs too near to such a device, the magnetic fields can generate an electric current on the cable that interferes with the signals exchanged by network devices. Jitter, crosstalk, and attenuation are all conditions that can affect the performance of a wired network, but they are not directly related to the cables' proximity to light fixtures.
Which of the following Windows command-line utilities produced the output shown here? a) ``` b) Interface: 192.168.2.24 --- 0x2 c) ``` 1. `ping` 2. `tracert` 3. `netstat` 4. `arp` 5. `hostname`
D. Running the `arp` utility with the `-a` parameter on a Windows system displays the contents of the Address Resolution Protocol (ARP) cache. The cache contains records of the Internet Protocol (IP) addresses on the network that `arp` has resolved into Media Access Control (MAC) addresses. The `ping`, `tracert`, `netstat`, and `hostname` utilities are not capable of producing this output.
Which of the following Windows tools uses Internet Control Message Protocol (ICMP) messages and manipulates IPv4 time-to-live values to illustrate the route packets take through an internetwork? a) `ping` b) `netstat` c) `route` d) `tracert` e) `nslookup` f) `hostname`
D. The Windows `tracert` tool transmits a series of ICMP messages with incrementing Time to Live (TTL) values, which identify each router on the path that the packets take through the network. `Ping` uses ICMP, but it does not manipulate TTL values. `Netstat`, `Route`, `Nslookup`, and `Hostname` do not use ICMP messages, nor do they manipulate TTL values when performing their normal functions.
