Infrastructure (4)

Question 1

Which of the following devices can you use to connect two multimode fiber-optic Ethernet networks in different buildings 2,000 meters apart using a single-mode fiber-optic cable segment running at the same speed, while maintaining a single collision domain?

Bridge

Router

Media converter

Answer 1

Media converter

A simple media converter is a physical layer device that can connect different types of network media together, as long as they have the same speed and duplex settings. Because the converter simply retransmits the signals, the single-collision domain is maintained. Bridges and switches are data link layer devices that create multiple-collision domains. Routers are network layer devices that create separate collision and broadcast domains

Question 2

At which layer of the Open Systems Interconnection (OSI) model do wireless range extenders operate?

Physical

Data link

Network

Answer 2

Physical

Wireless range extenders are physical layer devices that receive signals from wireless access points and network adapters and retransmit them, enabling devices to connect that are farther apart than the network would normally support. Because the extenders do not process the packets in any way, but just retransmit the signals, they do not operate at any layer above the physical

Question 3

Which of the following is another term for a multiport bridge?

Router

Switch

Hub

Answer 3

Switch

A switch is a data link layer device that essentially performs the function of a bridge for each device connected to one of its ports. It can therefore be described as a multiport bridge. Routers, hubs, and gateways are devices that operate at the network, physical, and application layers, respectively, so they cannot be described as bridges

Question 4

Which of the following devices enables two computers to communicate when they are using different protocols at each layer of the Open Systems Interconnection (OSI) reference model?

A router

A switch

A gateway

Answer 4

A gateway

A gateway enables two devices using different protocols to communicate by performing translation and conversion services for them. Routers, hubs, and switches all require the same protocol at some of the OSI model layers

Question 5

Which of the following statements about switches and routers are true? (Choose all correct answers.)

Routers operate at the network layer, whereas switches operate at the data link layer.

All of the devices connected to a switch are part of a single broadcast domain, whereas the networks connected to a router form separate broadcast domains.

Routers can communicate with each other and share information, but switches cannot.

Switches forward packets based on their hardware addresses, whereas routers forward packets based on their IP addresses.

Answer 5

Routers operate at the network layer, whereas switches operate at the data link layer.

All of the devices connected to a switch are part of a single broadcast domain, whereas the networks connected to a router form separate broadcast domains.

Switches forward packets based on their hardware addresses, whereas routers forward packets based on their IP addresses.

Routers are network layer devices that do not forward broadcast messages, so they create separate broadcast domains for each network. Switches do forward broadcasts, forming a single broadcast domain. Routers and switches can communicate using dedicated protocols. As data link layer devices, switches read only hardware addresses from packet frames; routers forward traffic based on the IP addresses in packets’ IP headers

Question 6

Ralph is installing an Ethernet local area network (LAN) for a small business with two offices on opposite sides of a courtyard. Ralph plans to run a multimode fiber-optic cable across the courtyard, but the budget is limited, and he can’t use fiber for the whole network. Therefore, he installs unshielded twisted pair (UTP) cable in the two offices, which have ten and twelve workstations, respectively. Which of the following devices should Ralph use to join the two UTP installations together into one LAN using the fiber-optic run across the courtyard, while keeping the cost to a minimum?

Media converters

Hubs

Switches

Answer 6

Media converters

Media converters will enable Ralph to join the multimode fiber-optic run to the UTP at both sides of the courtyard while maintaining a single network at minimum cost. Inexpensive small business hubs and switches cannot join different media together. Routers can join different media, but they are more expensive, and they would separate the installation into three separate networks

Question 7

Five computers are connected to the same switch, but only four are able to communicate with each other. Assuming that all of the hardware is functioning properly, which of the following could be a reason for the fifth computer’s communication problem?

The switch has the fifth computer connected to a VLAN different from that of the other four.

The network is experiencing a switching loop.

The fifth computer is experiencing an MTU black hole, whereas the other four computers are not.

Answer 7

The switch has the fifth computer connected to a VLAN different from that of the other four.

If the fifth computer is in a different VLAN from the other four, it would be unable to communicate with them. A switching loop would affect communication between all of the computers, not just the fifth one. An MTU black hole is a condition in which a system is unable to complete the Path MTU Discovery process, due to an intervening firewall. Because these five computers are all on the same LAN, they all have the same MTU, and Path MTU Discovery is not necessary. A virtual router would enable switched computers on different subnets to communicate with each other; it would not prevent them from communicating

Question 8

Which of the following network devices are “dumb”—that is, purely electrical devices with no electronic intelligence?

Hubs

Switches

Routers

Answer 8

Hubs

Hubs are network devices that simply receive signals through one port, electrically enhance them, and transmit them out through another port. Routers, switches, and bridges are capable of reading the signals and processing them, which classifies them as intelligent

Question 9

Which of the following statements about VLANs are true? (Choose all correct answers.)

All of the devices in a particular VLAN must be physically connected to the same switch.

A VLAN creates a limited broadcast domain on a switched network.

You must have VLANs on a switched network for communication between computers on different cable segments to occur.

A router is required for communication between VLANs.

Answer 9

A VLAN creates a limited broadcast domain on a switched network.

A router is required for communication between VLANs.

The computers in a single VLAN can be located anywhere on a switched network, regardless of the physical configuration of the switches. A broadcast message generated by a computer in a VLAN is transmitted to all of the other computers in that VLAN only, just as if the systems were physically located on a separate LAN or subnet. Unicast transmissions between computers on a switched network do not require VLANs because the switches create what amounts to a direct connection between the two systems. VLANs are needed only for communication processes that require using broadcasts, which, if transmitted without VLANs, would flood the network. Even though they are a purely logical construction, VLANs function just like physical subnets and require routers for communication between them. Routers are often integrated into layer 3 switches to enable communication between VLANs

Question 10

Which of the following explains why splitting a large switched Ethernet LAN into two LANs by adding a router can help to alleviate traffic congestion and improve performance? (Choose all correct answers.)

Adding a router reduces the amount of broadcast traffic on each of the two LANs.

Adding a router reduces the amount of unicast traffic on each of the two LANs.

Adding a router diverts traffic to an alternate path through the network.

Adding a router prevents computers on one LAN from communicating with computers on another LAN.

Answer 10

Adding a router reduces the amount of broadcast traffic on each of the two LANs.

Adding a router reduces the amount of unicast traffic on each of the two LANs.

Adding a router splits the Ethernet LAN into two LANs, creating two separate broadcast domains. Each computer, therefore, has a smaller number of broadcast messages to process. Because the network is split by the router, the amount of unicast traffic on each subnet is reduced

Question 11

A small business office currently has a 100Base-TX Ethernet network with a single 8-port hub. All of the hub ports are populated and the business owner wants to expand the network further. However, the hub does not have an uplink port. The owner has purchased a new hub, also with eight ports, which does have an uplink port, but he does not know how to connect them together. What must the owner do to install the new hub on the network?

Use a standard patch cable to connect a standard port on the existing hub to a standard port on the new hub.

Use a standard patch cable to connect a standard port on the existing hub to the uplink port on the new hub.

Purchase a crossover cable and use it to connect a standard port on the existing hub to the uplink port on the new hub.

Answer 11

Use a standard patch cable to connect a standard port on the existing hub to the uplink port on the new hub.

Standard hub ports have a crossover circuit, which ensures that the transmit signals at one end of the connection arrive at the receive pins at the other end. The uplink port in a hub bypasses the crossover circuit so that two connected hubs do not have crossover circuits that cancel each other out. A connection between a standard port and an uplink port, using a standard cable, results in a single crossover, which is correct wiring. Each of the other solutions results in either two crossovers or no crossovers, which is incorrect

Question 12

Which of the following tasks can you perform to split a large, switched local area network (LAN) into multiple broadcast domains? (Choose all correct answers.)

Replace one or more switches with hubs.

Install a firewall to filter broadcast traffic.

Enable the Spanning Tree Protocol (STP) on the switches.

Create VLANs in the switches.

Install routers on the network.

Answer 12

Create VLANs in the switches.

Install routers on the network.

By default, a switched LAN consists of a single broadcast domain. To create multiple broadcast domains, you can install routers to split the installation into two or more networks, because routers do not forward broadcasts. The other possibility is to create virtual LANs (VLANs) in the switches. Each VLAN is a separate broadcast domain. All of the other options would have no effect on the number of broadcast domains on the network

Question 13

Which of the following statements about bridges and switches is true?

Bridges and switches are network layer devices that use logical addressing to forward frames.

Bridges and switches are data link layer devices that use Media Access Control (MAC) addresses to forward frames.

Bridges and switches build their internal tables based on destination addresses and forward packets based on source addresses.

Answer 13

Bridges and switches are data link layer devices that use Media Access Control (MAC) addresses to forward frames.

Bridges and switches are data link layer devices that forward frames based on the destination MAC address contained in the frame. They operate in promiscuous mode, listening and processing all frames on each segment, and they build forwarding tables with this information. Forwarding tables are built based on source MAC addresses. Bridges are protocol independent; they are not involved with the upper layer protocols being carried on the LAN. Broadcast domains are defined by network layer devices, not data link layer devices

Question 14

Which of the following elements can be used to identify the devices in a particular VLAN? (Choose all correct answers.)

Hardware addresses

IP addresses

DNS names

Switch port numbers

Answer 14

Hardware addresses

Switch port numbers

Every network device has unique hardware addresses coded into the network interface adapter, and administrators can use these addresses to select the devices that will be part of a specific VLAN. IP addresses are layer 3 constructs and are not used to configure VLANs, which operate at layer 2. When VLANs are implemented inside the switch, selecting the ports to which specific computers are attached is a simple way to identify the computers in a particular VLAN. Although DNS names do uniquely identify computers on a network, DNS is an application layer process and has nothing to do with the switching and routing processes, which occur at the data link and network layers. Therefore, you cannot use DNS names to identify the computers in a VLAN

Question 15

Which of the following is a correct term describing the function of a switch?

Layer 2 router

Ethernet hub

Multiport bridge

Answer 15

Multiport bridge

A switch is best described as a multiport bridge because it reads the hardware addresses of incoming packets and forwards them out through the port for the destination node. Although a switch does function at layer 2 of the OSI model (the data link layer), it is not a router, which connects networks together at layer 3 (the network layer). Hubs and repeaters are physical layer (layer 1) devices that are not capable of performing the functions of a switch

Question 16

Which of the following is the primary reason why replacing hubs with switches on an Ethernet local area network (LAN) improves its performance?

Switches forward packets faster than hubs.

Switches do not forward broadcast transmissions.

Switches reduce the number of collisions on the network.

Answer 16

Switches reduce the number of collisions on the network.

The main reason why switches improve the efficiency of an Ethernet LAN is that they create a separate collision domain for each switched port, eliminating most collisions. Collisions result in packets having to be retransmitted, so fewer collisions means fewer retransmissions, which improves performance. Switches do not forward packets faster than hubs. Switches do forward broadcast transmissions. Switches do read hardware addresses, not IP addresses

Question 17

Which of the following is a correct definition of a collision domain?

A group of computers connected so that a broadcast transmission by any one device reaches all of the other devices

A group of devices connected by cable segments that are longer than the maximum length stated in the physical layer specification

A group of devices connected so that when two devices transmit at exactly the same time, a data collision occurs

Answer 17

A group of devices connected so that when two devices transmit at exactly the same time, a data collision occurs

A collision domain is a LAN with a shared network medium, so that two devices transmitting at the same time generate a signal quality error, also known as a collision. Ethernet LANs connected by hubs create a shared medium, whereas switched networks create a separate collision domain for each connected node. Routers create separate collision domains. A group of computers able to receive broadcasts is the definition of a broadcast domain, not a collision domain. Overlong cables can precipitate collisions but do not define a collision domain

Question 18

Which of the following terms are used to describe the device used to place calls on a Voice over Internet Protocol (VoIP) installation? (Choose all correct answers.)

Terminal

Gateway

Endpoint

PBX

Answer 18

Terminal

Endpoint

VoIP uses the terms terminal and endpoint to refer to the device with which users make calls, including computers and telephone handsets. A VoIP gateway is the device that provides the conduit between an IP network and the Public Switched Telephone Network (PSTN). A VoIP private branch exchange (PBX) is a device that switches calls between endpoints on the local IP network and provides access to external Internet lines

Question 19

Which of the following statements about hubs is not true?

Hubs are data link layer devices that connect network devices in a star or ring topology.

Hubs are physical layer devices that connect network devices in a star topology.

Hubs amplify and repeat signals received through one port out all other ports regardless of the destination.

Answer 19

Hubs are data link layer devices that connect network devices in a star or ring topology.

Hubs (or concentrators) are physical layer devices that amplify and repeat signals out all ports except the one through which the data was received, regardless of the destination. Hubs are used to physically connect end systems to a star topology. Hubs typically provide an internal crossover circuit connection. Uplink ports are used to extend the distance of a star network, forming a hierarchical star

Question 20

Which of the following statements about routers are true? (Choose all correct answers.)

Routers are network layer devices that use IP addresses to forward frames.

Routers are data link layer devices that use media access control (MAC) addresses to forward frames.

Routers build their internal tables based on destination MAC addresses and forward frames based on source MAC addresses.

Routers must support the network layer protocol implemented on the local area network (LAN).

Each port on a router defines a separate broadcast domain.

Answer 20

Routers are network layer devices that use IP addresses to forward frames.

Routers must support the network layer protocol implemented on the local area network (LAN).

Each port on a router defines a separate broadcast domain.

Routers are network layer devices that use IP addresses to forward frames, not MAC addresses. Routers are protocol dependent. They must support the network layer protocol being routed. As a network layer device, a router defines networks (or LANs) that represent a separate broadcast domain. Routers do not build their routing tables or forward frames using MAC addresses

Question 21

Which of the following hub types are supported by the 100Base-TX physical layer specification? (Choose all correct answers.)

Class I

Class II

Class III

Class IV

Answer 21

Class I

Class II

The 100Base-TX specification specifies two hub types: Class I and II. Class I hubs perform signal translation; Class II hubs do not. A network can have only one Class I hub per collision domain; a network can have two Class II hubs per collision domain. The other options do not exist

Question 22

Which of the following statements about routers is not true?

Routers can connect two or more networks with dissimilar data link layer protocols and media.

Routers can connect two or more networks with the same data link layer protocols and media.

Routers store and maintain route information in a local text file.

Answer 22

Routers store and maintain route information in a local text file.

Routers store and maintain route information in a routing table that is stored in memory, not in a local text file. All of the other statements about routers are true

Question 23

The network administrator for a small business is installing a computer to function as a firewall protecting their internetwork from Internet intrusion. At which of the following locations should the administrator install the firewall system?

Anywhere on the private internetwork, as long as the Internet is accessible

Between the Internet access router and the Internet service provider’s (ISP’s) network

Between the Internet access router and the rest of the private internetwork

Answer 23

Between the Internet access router and the rest of the private internetwork

The firewall is a conduit between the private network and the ISP’s network (which provides access to the Internet), through which all traffic must pass. This ensures that the firewall has the opportunity to examine every packet that passes between the private network and the Internet and filter out those that are not authorized. If the firewall was located in the midst of the private internetwork, it would be possible for Internet computers to bypass the firewall and communicate directly with the private systems. Placing the firewall on the far side of the router would put it on the ISP’s network, causing it to filter all of the ISP’s traffic and not just that destined for the private network. Installing the firewall at the ISP’s site would have the same effect as installing it on the far side of the router at the private network site

Question 24

What must you do to configure a firewall to admit File Transfer Protocol (FTP) traffic to the internal network using its default port settings? (Choose all correct answers.)

Open port 20

Open port 21

Open port 22

Open port 23

Open port 24

Answer 24

Open port 20

Open port 21

The FTP protocol uses two well-known ports, 20 and 21. A firewall must have both of these ports open to admit FTP traffic. FTP does not require ports 22, 23, or 24

Question 25

Proxy servers operate at which layer of the OSI reference model?

Network

Transport

Application

Answer 25

Application

A proxy server is an application layer service because it receives Internet service requests from client computers, reads the application layer protocol data in each request, and then generates its own request for the same service and transmits it to the Internet server the client specifies. Only an application layer service can read and process the application layer data in network packets. A proxy server cannot be a data link layer device because it can provide Internet access to an entire internetwork, while the data link layer is concerned with communications on a single subnet. Proxy servers cannot be network layer devices because the network layer handles all internetwork packets indiscriminately and is unaware of what application generated the data carried inside the packets. The transport layer is not involved in processing application data, so proxy servers cannot be said to function at the transport layer