2.1 Compare and contrast various devices, their features, and their appropriate placement on the network.

Which of the following terms is used to describe the method by which a firewall examines the port numbers in transport layer protocol headers? a. IP address filtering b. Service-dependent filtering c. Deep Packet Inspection (DPI) d. Next-Generation Firewall (NGFW)

B. Service-dependent filtering blocks traffic based on the port numbers specified in the transport layer header fields. Because port numbers represent specific applications, you can use them to prevent traffic generated by these applications from reaching a network. IP address filtering operates at the network layer. DPI scans the contents of packets, rather than their headers. NGFW defines a device with advanced protection capabilities; port number scanning is a basic firewall function.

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 that apply.) a. Adding a router reduces the amount of broadcast traffic on each of the two LANs. b. Adding a router reduces the amount of unicast traffic on each of the two LANs. c. Adding a router diverts traffic to an alternate path through the network. d. Adding a router prevents computers on one LAN from communicating with computers on another LAN.

A, B. 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.

Which two of the following functions is the multifunction device on a home or small office network known as a broadband router least likely to provide? (Choose two.) a. Wireless Access Point (WAP) b. Switch c. Proxy server d. DHCP server e. VPN headend

B. A bridge can split a single network into two collision domains, because it forwards only the packets that are destined for the other side of the bridge. The bridge forwards all broadcast packets, so it maintains a single broadcast domain. A hub maintains a single collision domain and a single broadcast domain. A switch creates a separate collision domain for each port, and a single broadcast domain for the entire network. A router creates two collision domains, but it does not forward broadcasts, so there are two broadcast domains as well. A repeater is a physical layer device that amplifies signals; it does not affect collision domains.

In local area networking, which of the following is not a type of bridge? a. Store and forward b. Routing c. Transparent d. Multiport

B. Bridges are data link layer (layer 2) devices. Routing is a network layer (layer 3) function, so it is not a type of bridge. A store-and-forward, or simple, bridge examines each packet and decides whether to forward it to the connected network. A transparent bridge compiles a database of forwarding information, based on the packets it has processed previously. A multiport bridge provides connections to multiple networks; a switch is a type of multiport bridge.

Which of the following physical network devices can conceivably be implemented as software in a computer's operating system? (Choose all that apply.) a. Hub b. Switch c. Router d. Firewall

C, D. Most operating systems are capable of functioning as routers or firewalls. To route traffic, the system must have two network connections. A software firewall can be part of a computer's routing functionality, or it can be a stand-alone firewall that protects only the local system. Computers cannot function as hubs or switches, because multiple ports would be required, and standard network adapters do not implement those functions.

Which of the following is the true definition of the term modem? a. A device that connects a computer to the Public Switched Telephone Network (PSTN) b. A device that connects a Local Area Network (LAN) to the Internet c. A device that converts analog signals to digital signals and back again d. A device that connects a Local Area Network (LAN) to a Wide Area Network (WAN)

C. A modem (modulator/demodulator) is any device that converts analog signals to digital signals and digital signals back to analog signals. The digital device does not have to be a computer, and the analog device does not have to be the PSTN. There are many devices that are incorrectly referred to as modems, such as devices that connect a digital LAN to a digital WAN or all-digital devices that connect computers to the Internet.

A Wireless Access Point (WAP) enables computers equipped with wireless network interface adapters to function in which of the following topologies? a. Star b. Ad hoc c. Bus d. Infrastructure

D. A WAP is a device with a wireless transceiver that also connects to a standard cabled network. Wireless computers communicate with the WAP, which forwards their transmissions over the network cable. This is called an infrastructure topology. A star or bus network requires the computers to be physically connected to the network cable, and an ad hoc topology is one in which wireless computers communicate directly with one another.

Which of the following statements about switches and routers are true? (Choose all that apply.) a. Routers operate at the network layer, whereas switches operate at the data link layer. b. 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. c. Routers can communicate with each other and share information, but switches cannot. d. Switches forward packets based on their hardware addresses, whereas routers forward packets based on their IP addresses.

A, B, D. 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.

A multilayer switch typically functions at which layers of the OSI reference model? (Choose two.) a. Data link b. Network c. Transport d. Application

A, B. All switches operate at the data link layer of the OSI model, but multilayer switches usually also function as routers, which are network layer devices. They are not usually transport or application layer devices.

Which of the following are methods typically used by Intrusion Detection Systems (IDSs) to analyze incoming network traffic? (Choose all that apply.) a. Anomaly-based detection b. Behavior-based detection c. Signature-based detection d. Statistic-based detection

A, C. IDSs can use anomaly-based detection to identify deviations from a known baseline of trustworthiness, or signature-based detection to locate specific malicious byte or instruction sequences. Behavior-based and statistic-based detection are not typical IDS methods.

Which of the following problems is the Spanning Tree Protocol (STP) intended to prevent? (Choose all that apply.) a. Broadcast storms b. Late collisions c. Bridging loops d. Crosstalk

A, C. STP disables redundant links between switches that can allow packets to circulate endlessly around the network. This is called a bridging loop. As a result of a bridging loop, the network can be flooded with broadcast traffic, which is called a broadcast storm. STP does nothing to prevent late collisions, which is an Ethernet timing problem, or crosstalk, which is a cabling fault.

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 that apply.) a. Terminal b. Gateway c. Endpoint d. PBX

A, C. 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.

Which of the following statements about routers are true? (Choose all that apply.) a. Routers are network layer devices that use IP addresses to forward frames. b. Routers are data link layer devices that use Media Access Control (MAC) addresses to forward frames. c. Routers build their internal tables based on destination MAC addresses and forward frames based on source MAC addresses. d. Routers must support the network layer protocol implemented on the Local Area Network (LAN). e. Each port on a router defines a separate broadcast domain.

A, D, E. 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.

Which of the following best describes the function of a firewall? a. A device located between two networks that enables administrators to restrict incoming and outgoing traffic b. A device that connects two networks together, forwarding traffic between them as needed c. A device that enables Internet network clients with private IP addresses to access the Internet d. A device that caches Internet data for subsequent use by internal network clients

A. A firewall is a filter that can prevent dangerous traffic originating on one network from passing through to another network. A device that connects two networks together and forwards traffic between them is a router, not a firewall. A device that enables Internet network clients with private IP addresses to access the Internet is a description of a NAT router or a proxy server, not a firewall. A device that caches Internet data is a proxy server or caching engine, not a firewall.

Which of the following is typically not an example of the Internet of Things (IoT)? a. A key fob that unlocks your car b. A smartphone home automation app c. A remotely monitored cardiac pacemaker d. A seismic early warning system

A. A key fob that unlocks your car is typically a short-range radio or infrared device that does not use the Internet for its communications. Each of the other examples describes a device with an IP address that uses the Internet to communicate with a controller or monitoring

Which of the following devices can also be described as a multiport repeater? a. Hub b. Bridge c. Switch d. Router

A. A repeater is a physical layer device that regenerates incoming signals and retransmits them. A hub is a type of repeater that receives data through any one of its multiple ports and retransmits the data out through all of its other ports. Bridges and switches are data link layer devices, and routers are network layer devices. None of these three can be described as multiport repeaters.

Which of the following switch types immediately forwards frames after looking at only the destination address? a. Cut-through b. Source route c. Store-and-forward d. Destination

A. Cut-through switches are fast, because they look at only the first six bytes (the destination Media Access Control, or MAC, address) when forwarding a frame. They do not perform a cyclical redundancy check (CRC) on the entire frame's contents prior to forwarding it out a port leading to the destination. Source route is a bridging technique in which the source host, not the switch, determines the path a frame will take through a network to reach a destination. Store-and-forward switches take in the entire frame and verify its contents by performing a CRC calculation before forwarding it. There is no switch called a destination switch.

Which of the following network devices are "dumb"—that is, purely electrical devices with no electronic intelligence? a. Hubs b. Switches c. Routers d. Bridges

A. 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.

Which of the following statements about hubs is not true? a. Hubs are data link layer devices that connect network devices in a star or ring topology. b. Hubs amplify and repeat signals received through one port out all other ports regardless of the destination. c. Hubs are physical layer devices that connect network devices in a star topology. d. Hubs provide internal crossover circuits and use uplink ports to form a hierarchical star.

A. Hubs 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.

Which of the following devices perform essentially the same function? (Choose two.) a. Hubs b. Bridges c. Switches d. Routers

B, C. A switch is essentially a multiport bridge. Both switches and bridges process incoming packets by scanning their data link layer hardware addresses and forwarding the packets out the port connected to the destination system. The primary difference between them is that switches have many ports, whereas bridges have only two. Hubs and routers are physical layer and network layer devices, respectively, and perform different functions.

ive 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? a. The switch has the fifth computer connected to a Virtual Local Area Network (VLAN) that's different from that of the other four. b. The network is experiencing a switching loop. c. The fifth computer is experiencing an MTU black hole, whereas the other four computers are not. d. There is a virtual router between the fifth computer and the other four.

A. 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.

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 cannot use fiber for the whole network. Therefore, he installs Unshielded Twisted Pair (UTP) cable in the two offices, which have 10 and 12 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? a. Media converters b. Hubs c. Switches d. Routers

A. 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.

Which of the following types of systems are frequently used to collect information from Intrusion Detection Systems (IDSs)? a. SIEM b. NGFW c. RADIUS d. VoIP

A. Security Information and Event Management (SIEM) systems can function as a central clearinghouse for information gathered by IDSs and other security processes. Next-Generation Firewall (NGFW), Remote Authentication Dial-In User Service (RADIUS), and Voice over IP (VoIP) are not systems that collect IDS information.

Which of the following devices run exclusively at the physical layer of the Open Systems Interconnection (OSI) model? (Choose all that apply.) a. Routers b. Hubs c. Repeaters d. Switches

B, C. A repeater is a physical layer device that amplifies the signals entering it and transmits them again. A hub is a physical layer device that propagates incoming signals out through all of its ports. Switches and routers have physical layer elements but are primarily data link and network layer devices, respectively.

Which of the following statements about hubs and switches are true? (Choose all that apply.) a. Hubs operate at the physical layer, whereas switches operate at the network layer. b. All of the devices connected to a hub are part of a single collision domain, whereas each device connected to a switch has its own collision domain. c. There are switches available with network layer functionality, but there are no hubs with that capability. d. Switches create a separate broadcast domain for each connected device, whereas hubs create a single broadcast domain for all of the connected devices.

B, C. Hubs operate at the physical layer and switches at the data link layer. Hubs and switches both create a single broadcast domain for all of the connected devices. Switches create a separate collision domain for each connected device, whereas hubs create a single collision domain. There are switches (but not hubs) with network layer (layer 3) functionality.

5. Which of the following devices can split a single network into two collision domains while maintaining a single broadcast domain? a. Hub b. Bridge c. Switch d. Router e. Repeater

B. A bridge can split a single network into two collision domains, because it forwards only the packets that are destined for the other side of the bridge. The bridge forwards all broadcast packets, so it maintains a single broadcast domain. A hub maintains a single collision domain and a single broadcast domain. A switch creates a separate collision domain for each port, and a single broadcast domain for the entire network. A router creates two collision domains, but it does not forward broadcasts, so there are two broadcast domains as well. A repeater is a physical layer device that amplifies signals; it does not affect collision domains.

Which of the following is another term for a multiport bridge? a. Router b. Switch c. Hub d. Gateway

B. 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.

Which of the following statements about bridges and switches is true? a. Bridges and switches are network layer devices that use logical addressing to forward frames. b. Bridges and switches are data link layer devices that use Media Access Control (MAC) addresses to forward frames. c. Bridges and switches build their internal tables based on destination addresses and forward packets based on source addresses. d. Bridges and switches must support the network layer protocol implemented on the Local Area Network (LAN). e. Each port on a bridge or switch defines a separate broadcast domain.

B. 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.

Virtual Local Area Networks (VLANs) create the administrative boundaries on a switched network that are otherwise provided by which of the following devices? a. Hubs b. Routers c. Firewalls d. Bridges

B. Connecting subnets with routers at the network layer maintains the data link layer administrative boundaries that prevent broadcast transmissions from being propagated throughout the entire internetwork. Switching eliminates those data link layer boundaries, and administrators can use VLANs to simulate them. Because hubs propagate all of the traffic they receive out through all of their ports indiscriminately, they create no administrative boundaries. Firewalls are filtering devices that protect networks against malicious traffic; their functions are not related to VLANs. Switches are essentially multiport bridges that forward incoming traffic only to the device for which it is destined. Therefore, bridges are more closely related to eliminating administrative boundaries than to establishing them.

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? a. Use a standard patch cable to connect a standard port on the existing hub to a standard port on the new hub. b. Use a standard patch cable to connect a standard port on the existing hub to the uplink port on the new hub. c. Purchase a crossover cable and use it to connect a standard port on the existing hub to the uplink port on the new hub. d. Purchase a second new hub with an uplink port to replace the old one and use a standard patch cable to connect the two uplink ports together.

B. 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.

Which of the following does a switch use to forward incoming packets out through the correct ports? a. IP addresses b. MAC addresses c. DNS names d. MTU values

B. Switches use Media Access Control (MAC) addresses to identify the ports associated with specific hosts. The switch reads the destination MAC address from each incoming packet and forwards it out through the port associated with that address. Switches are data link layer devices, so they do not use IP addresses or DNS names to forward packets. The Maximum Transmission Unit (MTU) value specifies the maximum size of data link layer frames; the switch does not use it to forward packets.

Which of the following is not one of the five functional levels associated with a distributed control system such as Supervisory Control and Data Acquisition (SCADA) systems? a. Field level b. Remote access c. Direct control d. Plant supervisory e. Production control f. Production scheduling

B. The five functional levels in a distributed control system such as SCADA are field level, direct control, plant supervisory, production control, and production scheduling. Remote access is not one of the levels.

Which of the following is the correct term for the process by which the Spanning Tree Protocol (STP) on a switch evaluates the paths through the network and places each port in the forwarding or blocking state? a. Assimilation b. Convergence c. Tree-building d. Listening

B. The process by which STP populates its database with information about each port in a switch and designates the ports as forwarding or blocking is called convergence. Assimilation, tree-building, and listening are not terms for STP path evaluation.

Which of the following is a correct term describing the function of a switch? a. Layer 2 router b. Ethernet hub c. Multiport bridge d. Layer 3 repeater

C. 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.

Which of the following is something that only a firewall capable of stateful packet inspection can do? a. Filter traffic-based port numbers b. Block traffic destined for specific IP addresses c. Scan transport layer header fields for evidence of SYN floods d. Block all TCP traffic from entering a network

C. A firewall that supports stateful packet inspection examines other network and transport layer header fields, looking for patterns that indicate damaging behaviors, such as IP spoofing, SYN floods, and teardrop attacks. Port number filtering is the most commonly used form of packet filtering; it is not the same as stateful packet inspection. Blocking traffic based on IP addresses prevents specific systems from accessing a network; stateful packet inspection is a much more complicated operation. Packet filtering based on protocol identifiers enables you to block TCP traffic; this is not stateful packet inspection.

Ralph is a freelance network consultant installing a three-node small business network. The computers are all in the same room and use wired Ethernet to connect to the switched ports of a multifunction device. The device also functions as a Network Address Translation (NAT) router for a cable modem connection to the Internet. NAT provides a measure of security, but Ralph wants to be sure that the network is protected from unauthorized Internet traffic and attacks against open ports. Which of the following solutions would enable Ralph to accomplish this goal with the minimum cost to the client? a. Install a hardware firewall between the multifunction device and the cable modem. b. Install an Intrusion Prevention System (IPS) between the multifunction device and the cable modem. c. Install a personal firewall on each of the computers. d. Connect an Intrusion Detection System (IDS) to one of the switched ports in the multifunction device. e. Use a port scanner to monitor the traffic entering the open ports on the computers.

C. A personal firewall is an inexpensive way to protect an individual computer from Internet incursions. Installing a hardware firewall is a complex and expensive solution, not suitable for a small network. An IPS is a relatively expensive solution, suitable for larger networks. An IDS is also expensive, and connecting it to a switched port would not enable it to protect the other computers on the network. A port scanner is a device that performs scans on demand. It does not continuously monitor ports, and it does nothing to protect them.

Which of the following devices is used to physically connect computers in the same Virtual Local Area Network (VLAN)? a. A bridge b. A hub c. A switch d. A router

C. Replacing routers with switches turns an internetwork into a single large subnet, and VLANs exist as logical elements on top of the switching fabric. Although VLANs are the functional equivalent of network layer subnets, the systems in a single VLAN are still connected by switches, not routers. Bridges connect network segments at the data link layer and selectively forward traffic between the segments. However, bridges do not provide a dedicated connection between two systems like a switch does, and they do not make it possible to convert a large, routed internetwork into a single switched network. Therefore, they have no role in implementing VLANs. Hubs are physical layer devices that propagate all incoming traffic out through all of their ports. Replacing the routers on an internetwork with hubs would create a single shared network with huge amounts of traffic and collisions. Hubs, therefore, do not connect the computers in a VLAN.

Which of the following bridging types has never been used on Ethernet Local Area Networks (LANs)? a. Store and forward b. Transparent c. Source route d. Multiport

C. Source route bridging was a technique used on Token Ring (and not Ethernet) networks, in which a Routing Information Field (RIF) in the packet header identified the network segments the packet should follow to reach its destination. Store and forward, transparent, and multiport bridges have all been used on Ethernet networks.

Ralph has been hired by a company to redesign its Local Area Network (LAN). Right now, it has a single 100 Mbps Ethernet LAN with 40 users and 2 shared servers, all connected through 3 hubs. The users on the network must be able to share files with one another and also access the shared servers. The users are complaining that the network is too slow. Management states that cost is a factor that must be considered. Which of the following upgrade scenarios should Ralph recommend in this situation? a. Split the network into smaller segments with dedicated hubs as opposed to shared hubs. b. Split the network into two routed LANs with 20 users each. c. Replace the hubs with switches to define separate collision domains and filter unnecessary traffic from each segment. d. Replace the hubs with a layer 3 switch and define two Virtual LANs (VLANs) with 20 users each.

C. The best choice is to replace the hubs with switches, since the network is relatively small, and cost is an issue. On the existing network, all users share the same 100 Mbps communication channel, and each computer must take turns transmitting. By replacing the hubs with switches, you provide each computer with a dedicated 100 Mbps connection to the switch, while reducing unnecessary traffic and collisions on the network. There is no such thing as a dedicated hub. Splitting the network into two routed LANs is not the best solution, because all users must share information on a constant basis. Also, cost is a factor, and routers are more expensive than switches. Replacing the hubs with a layer 3 switch and defining two VLANs with 20 users each is not a reasonable solution, because layer 3 switches are very expensive.

Which of the following is the primary reason why replacing hubs with switches on an Ethernet Local Area Network (LAN) improves its performance? a. Switches forward packets faster than hubs. b. Switches do not forward broadcast transmissions. c. Switches reduce the number of collisions on the network. d. Switches read the IP addresses of packets, not the hardware addresses.

C. 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.

Which of the following tasks can you perform to split a large, switched Local Area Network (LAN) into multiple broadcast domains? (Choose all that apply.) a. Replace one or more switches with hubs. b. Install a firewall to filter broadcast traffic. c. Enable the Spanning Tree Protocol (STP) on the switches. d. Create Virtual Local Area Networks (VLANs) in the switches. e. Install routers on the network.

D, E. 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 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.

Which of the following is a correct definition of a collision domain? a. A group of Local Area Networks (LANs), connected by routers, that enables any node to transmit to any other node b. A group of computers connected so that a broadcast transmission by any one device reaches all of the other devices c. A group of devices connected by cable segments that are longer than the maximum length stated in the physical layer specification d. A group of devices connected so that when two devices transmit at exactly the same time, a data collision occurs

D. 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

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. A router b. A switch c. A hub d. A gateway

D. 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.

Which of the following devices can you use to connect two multimode fiber-optic Ethernet networks in different buildings 2000 meters apart using a single-mode fiber-optic cable segment running at the same speed, while maintaining a single collision domain? a. Bridge b. Switch c. Router d. Media converter

D. 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.

Which of the following technologies associated with the Internet of Things (IoT) is often used to identify pets using embedded chips? a. Z-wave b. Bluetooth c. NFC d. RFID

D. Radio-frequency identification (RFID) uses tags containing data, frequently embedded in pets, which can be read using electromagnetic fields. Z-wave is a short-range wireless technology, frequently used for home automation. Bluetooth is a short-range wireless protocol, frequently used for computer peripherals and Personal Area Networks (PANs). Near-field communication (NFC) provides wireless communication over ranges of 4 cm or less, and it is often used for payment systems.

Which of the following statements about the Spanning Tree Protocol (STP) is not true? a. STP operates at the data link layer of the OSI model. b. STP is implemented in switches. c. STP prevents traffic from circulating endlessly around a network. d. STP compiles a database containing the IP addresses of connected devices.

D. STP operates at the data link layer of the OSI model, so it works with hardware addresses, not IP addresses. Switches use STP to prevent redundant links from causing traffic loops on the network.

Which of the following criteria does a firewall capable of service-dependent filtering use to block traffic? a. Hardware addresses b. Protocol identifiers c. IP addresses d. Port numbers

D. Service-dependent filtering blocks traffic based on the port numbers specified in the transport layer header fields. Because port numbers represent specific applications, you can use them to prevent traffic generated by these applications from reaching a network. IP address filtering enables you to limit network access to specific computers; it is not service dependent. Filtering based on hardware addresses provides the same basic functionality as IP address filtering, but it is more difficult to spoof hardware addresses than IP addresses. Filtering by protocol identifier enables you to block all traffic using TCP or UDP; it is not service dependent.

Small Office Home Office (SOHO) networks typically use a multifunction connectivity device that can perform all but which one of the following functions? a. DHCP b. DNS c. Switch d. Router e. Hub f. NAT router g. Access Point (AP)

E. SOHO multifunction devices typically function as routers connecting the local network to an Internet Service Provider (ISP), switches providing wired connections to host devices, Dynamic Host Configuration Protocol (DHCP) servers assigning IP addresses, Domain Name System (DNS) servers resolving names into IP addresses, Network Address Translation (NAT) routers providing hosts with private IP addresses access to the Internet, and APs providing wireless devices with access to the network. They do not function as hubs.

Which of the following are available as Internet of Things (IoT) devices? a. Refrigerators b. Doorbells c. Thermostats d. Speakers e. All of the above

E. The IoT consists of devices that are ordinarily passive, but which have been made intelligent by configuring them to participate on an IP network. All of the devices listed are available as "smart" devices that enable remote users to interact with them over the Internet.