Practice (4) Flashcards
You are designing a new wireless network based on the IEEE 802.11n standard. The equipment you have selected supports both the 2.4 GHz and 5 GHz frequencies, and you are undecided about which one to use. Which of the following are possible reasons why the 5 GHz frequency tends to perform better than the 2.4 GHz frequency on a wireless LAN? (Choose all correct answers.)
The 5 GHz frequency has more channels than the 2.4 GHz frequency.
The 5 GHz frequency conflicts with fewer common household devices than the 2.4 GHz frequency.
The 5 GHz frequency transmits at faster speeds than the 2.4 GHz frequency.
The 5 GHz frequency supports longer ranges than the 2.4 GHz frequency.
The 5 GHz frequency has more channels than the 2.4 GHz frequency.
The 5 GHz frequency conflicts with fewer common household devices than the 2.4 GHz frequency.
The 5 GHz frequency transmits at faster speeds than the 2.4 GHz frequency.
The 5 GHz frequency has 23 channels available in the United States, whereas the 2.4 GHz frequency has only 11. Many household devices, such as cordless telephones, use the 2.4 GHz frequency band, but relatively few devices use the 5 GHz band. Higher frequencies typically support faster transmission speeds, because with all other conditions equal, they can carry more data in the same amount of time. The 5 GHz frequency typically has a shorter range than 2.4 GHz, because it is less able to penetrate barriers
Which of the following server applications uses two well-known port numbers, one for control traffic and one for data traffic?
FTP
SNMP
NTP
FTP
The File Transfer Protocol (FTP) uses two port numbers. It uses the first, port 21, for a control connection that remains open during the entire client-server session. The second port, 20, is for a data connection that opens only when the protocol is actually transferring a file between the client and the server. Network Time Protocol (NTP), Simple Network Management Protocol (SNMP), and Hypertext Transfer Protocol (HTTP) all use a single port on the server
You are configuring the computers on a new network, and you have been given the network address 10.26.0.0/13. Which of the following subnet mask values must you use when configuring the computers?
- 248.0.0
- 252.0.0
- 254.0.0
255.248.0.0
The 13-bit prefix indicated in the network address will result in a mask with 13 ones followed by 19 zeroes. Broken into 8-bit blocks, the binary mask value is as follows:
11111111 11111000 00000000 00000000
Converted into decimal values, this results in a subnet mask value of 255.248.0.0
You are testing a twisted pair cable run using a tone generator and locator. When you apply the tone generator to each of the first seven wires at one end of the cable, you successfully detect a tone on the corresponding pin at the other end. However, when you connect the tone generator to the eighth wire, you fail to detect a tone at the other end. Which of the following fault types have you discovered?
Short circuit
Open circuit
Split pair
Open circuit
The failure to detect a tone on the eighth wire indicates that there is either a break in the wire somewhere inside the cable or a bad pin connection in one or both connectors. This type of fault is called an open circuit. None of the other three options are faults that manifest as described. A short circuit 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
Which of the following functions are defined as occurring at the session layer of the Open Systems Interconnection (OSI) model? (Choose all correct answers.)
Data encryption
Dialog control
Datagram routing
Dialog separation
Dialog control
Dialog separation
The session layer is responsible for creating and maintaining a dialog between end systems. This dialog can be a two-way alternate dialog that requires end systems to take turns transmitting, or it can be a two-way simultaneous dialog in which either end system can transmit at will. The session layer functions are called dialog control and dialog separation. Data encryption is performed at the presentation layer, and datagram routing occurs at the network layer
You are working your company’s IT help desk, and you have had several calls from users who are reporting problems with their Voice over IP and streaming video connections. In each case, the audio or video connection experiences frequent dropouts in sound or video, causing frustrating interruptions. Which of the following terms describes a connectivity problem on a wired network that could cause these symptoms?
Jitter
Latency
Bottleneck
Jitter
When individual packets in a data stream are delayed, due to network congestion, different routing, or queuing problems, the resulting connectivity problem is called jitter. While this condition might not cause problems for asynchronous applications, real-time communications, such as Voice over IP or streaming video, can suffer interruptions from which the phenomenon gets its name. Latency describes a generalized delay in network transmissions, not individual packet delays. Attenuation is the weakening of a signal as it travels through a network medium. A bottleneck is a condition in which all traffic is delayed, due to a faulty or inadequate component. None of these three options would account for the problems reported by the users
You are a consultant with a client who wants to have you install a wireless network with the highest throughput currently available. What can you tell your client is the fastest speed achievable by a wireless LAN using the currently ratified IEEE 802.11 standards?
54 Mbps
600 Mbps
1.3 Gbps
1.3 Gbps
The 802.11ac standard defines a wireless LAN running at speeds of up to 1.3 gigabits per second (Gbps). None of the other 802.11 standards define networks running at speeds beyond 600 Mbps. There is no currently ratified IEEE 802.11 standard that enables speeds of 2.6 Gbps
A private network uses unregistered IP addresses that are not accessible from the Internet. For computers on the private network to access Internet servers, there must be a device that substitutes registered IP addresses for the unregistered ones. Which of the following devices are capable of performing this kind of IP address substitution? (Choose all correct answers.)
RADIUS server
NAT router
UTM appliance
Proxy server
NAT router
Proxy server
Network address translation (NAT) is a network layer service, typically integrated into a router, that converts the private IP addresses in all of a client’s Internet transmissions to a registered IP address. NAT therefore works for all applications. A proxy server is an application layer device that performs the same type of conversion but only for specific applications. A Remote Authentication Dial-In User Service (RADIUS) server can provide authentication, authorization, and accounting services for remote access servers, but it does not convert IP addresses. A unified threat management (UTM) appliance typically performs virtual private network (VPN), firewall, and antivirus functions. It too does not convert IP addresses
A user calls you at the technical support desk in the computer store where you work. He is installing a home network and is having trouble configuring the IP addresses for his computers. He starts reading off a list of the network addresses he has tried to use. Which of the following are valid IPv4 network addresses that the user can conceivably use to configure his computers? (Choose all correct answers.)
- 1.1.0
- 34.0.0
- 256.77.0
- 6.87.0
- 1.1.0
- 34.0.0
- 1.1.0 and 9.34.0.0 are both valid IPv4 network addresses. IPv4 addresses with first byte values from 224 to 239 are Class D addresses, which are reserved for use as multicast addresses. Therefore, the user cannot use 229.6.87.0 for his network. 103.256.77.0 is an invalid address because the value 256 cannot be represented by an 8-bit binary value
Which of the following terms refers to a routing protocol that relies on hop counts to measure the efficiency of routes through an internetwork?
Link state protocol
Distance vector protocol
Edge gateway protocol
Distance vector protocol
Distance vector protocols rely on hop counts—that is, the number of routers between a source and a destination—to evaluate the efficiency of routes. Link state protocols use a different type of calculation, usually based on Dijkstra’s algorithm. The terms interior gateway protocol and edge gateway protocol do not refer to the method of calculating routing efficiency
You have been hired by a client to connect two local area networks together, which are in different buildings 500 meters apart. The cable type you use must support Gigabit Ethernet data rates of 1000 megabits per second (Mbps) and provide a high level of resistance to electromagnetic interference (EMI). Which of the following cable types can you choose to meet the client’s needs? (Choose all correct answers.)
Single-mode fiber-optic cable
Thin coaxial cable
Multimode fiber-optic cable
Shielded twisted pair (STP) cable
Unshielded twisted pair (UTP) cable
Single-mode fiber-optic cable
Multimode fiber-optic cable
Any type of fiber-optic cable will satisfy the client’s requirements. Fiber-optic cable supports the required 1000 Mbps data rate and can connect networks that are 500 meters apart. Fiber-optic cable is also immune to EMI. Although both multimode and single-mode fiber would meet the corporation’s general needs, multimode is substantially less expensive than single-mode fiber. Twisted pair wiring (STP or UTP) meets the data rate, but it does not support connections longer than 100 meters. Thin coaxial cable does not support the data rate or distances longer than 185 meters
You receive a call at the IT help desk from a user who has recently moved to a new office in the company building, down the hall from her old one. Since the move, she has only been able to access the company’s wireless network with her laptop intermittently. The network is based on 802.11n equipment, and it is using the 2.4 GHz frequency and the WPA2 security protocol. The user never had a problem in her previous office location. Which of the following could not possibly be the cause of her problem? (Choose all correct answers.)
The user’s laptop is connecting to the wrong SSID.
The user’s laptop is configured to use the 5 GHz frequency.
The user’s new office is farther from the access point than her old one.
There are more intervening walls between the user’s new office and the access point.
The user’s laptop is configured with the wrong WPA2 passphrase.
The user’s new office is farther from the access point than her old one.
There are more intervening walls between the user’s new office and the access point.
An incorrect frequency, SSID, or WPA2 passphrase would prevent the user’s laptop from ever connecting to the network, so these cannot be the cause of the problem. Greater distance from the access point or interference from intervening walls can both cause a weakening of wireless signals, which can result in the intermittent connectivity that the user is experiencing
Which of the following statements about static routing are not true? (Choose all correct answers.)
Static routes are automatically added to the routing table by routing protocols when a new network path becomes available.
Static routes are manually configured routes that administrators must add, modify, or delete when a change in the network occurs.
Static routes are a recommended solution for large internetworks with redundant paths to each destination network.
Static routes are a recommended solution for small internetworks with a single path to each destination network.
Static routes adapt to changes in the network infrastructure automatically.
Static routes are automatically added to the routing table by routing protocols when a new network path becomes available.
Static routes are a recommended solution for large internetworks with redundant paths to each destination network.
Static routes adapt to changes in the network infrastructure automatically.
Static routes are not automatically added to the routing table by routing protocols and do not automatically adapt to changes in the network. They are therefore not recommended for large internetworks with redundant paths between networks. Administrators must manually add, modify, or delete static routes when a change in a network occurs. For this reason, static routes are recommended only for use in small networks without multiple paths to each destination
Which layer of the Open Systems Interconnection (OSI) model has its own logical addressing system and is responsible for routing packets from one network to another?
Physical
Data link
Network
Transport
Session
Presentation
Application
Network
Network layer protocols specify logical addresses, such as IP addresses, for end system communication. They also use those addresses to route packets to destinations on other networks. The physical layer defines standards for physical and mechanical characteristics of a network. The data link layer uses media access control (MAC) or hardware addresses, not logical addresses. The transport layer uses port numbers, not logical addresses. Session layer protocols create and maintain a dialog between end systems. Presentation layer protocols are responsible for the formatting, translation, and presentation of information. The application layer provides an entry point for applications to access the protocol stack and prepare information for transmission across a network
There are several marketing consultants working in your office for the first time, and they have approached you because they are unable to connect to the company’s 802.11g wireless network with their laptops. They are selecting the correct SSID from the Available Networks list, but they still cannot connect, and there are no error messages of any kind. Which of the following tasks should you perform first to try to resolve the problem?
Examine the area where the consultants are working for possible sources of signal interference.
Change the frequency used by the wireless access point from 2.4 GHz to 5 GHz.
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 you to discover the source of the problem. Channel overlap is a problem that you would check and resolve at the access point, not at 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’s SSID, so this is not likely to be the problem
