2.3 Given a scenario, configure and deploy common Ethernet switching features.

Which of the following is not a method of traffic shaping? a. Rate limiting b. WAN optimization c. Bandwidth throttling d. Self-limiting

B. WAN optimization is not a form of traffic shaping, because it compresses data streams and transmits incremental file updates. Traffic shaping uses techniques like rate limiting, bandwidth throttling, and self-limiting to delay the transmission of specific types of data packets to optimize network performance.

Which of the following network layer protocols includes a Time to Live (TTL) field? (Choose all that apply.) a. IPv4 b. IPv6 c. ICMP d. IGMP

A, B. The Internet Protocol (IP) in both of its versions (IPv4 and IPv6) includes a TTL field in its message header that limits the number of times a packet can be routed on a network. Each router processing the packet reduces the TTL value by one until it reaches zero, after which it is discarded. The Internet Control Message Protocol (ICMP) and the Internet Group Management Protocol (IGMP) do not have a TTL field.

Which of the following cable types is needed to connect an MDI port on a workstation to an MDI-X port on an Ethernet switch? a. A crossover twisted pair cable b. A straight-through twisted pair cable c. A coaxial cable d. A single-mode fiber optic cable e. A multimode fiber optic cable

B. When connecting an MDI port to an MDI-X port, the necessary crossover circuit is implemented in the MDI-X port. Therefore, the connection needs a straight-through cable, and there is no need for a crossover cable. MDI and MDI-X ports are used only with twisted pair cables, so there is no need for coaxial or fiber optic cables.

Which of the following features helps to protect network switches from attacks related to the Spanning Tree Protocol (STP)? (Choose all that apply.) a. BPDU guard b. Root guard c. DHCP snooping d. Geofencing

A, B. Bridge Protocol Data Units (BPDUs) are messages that switches running the STP exchange to learn about the available paths through a switched network and the states of other switches. Switches should only receive BPDUs through ports that are connected to other switches. BPDU guard is a feature that prevents BPDU messages from arriving through ports connected to end systems, such as computers, thus preventing an attacker from manipulating the STP topology. A root guard affects the behavior of the STP by enforcing the selection of root bridge ports on a switched network. Without root guards, there is no way for administrators to enforce the topology of a network with a redundant switching fabric.

Which of the following modifications occur when you configure the native Virtual Local Area Network (VLAN) on your network switches to use 802.1q tagging? (Choose all that apply.) a. Double-tagged packets are prevented. b. BPDU guards are applied. c. Root guards are applied. d. Trunk traffic is routed, not switched.

A, B. To join ports on different switches into one VLAN, you designate a trunk port on each switch for the traffic between switches. Initially, the native VLAN uses the default VLAN1 for trunk traffic, and that traffic is left untagged. Untagged traffic is susceptible to attacks using double-tagged packets. When you configure the native VLAN to use tagging, this makes it impervious to double-tagging. Changing the native VLAN does not create root guards or Bridge Protocol Data Unit (BPDU) guards, and all traffic continues to be switched, not routed.

Which of the following cable types can be used to connect an MDI port on a workstation to an Auto-MDI-X port on an Ethernet switch? (Choose all that apply.) a. A crossover twisted pair cable b. A straight-through twisted pair cable c. A coaxial cable d. A single-mode fiber optic cable e. A multimode fiber optic cable

A, B. When connecting an MDI port to an Auto-MDI-X port, it is possible to use either a straight-through or a crossover cable because the Auto-MDI-X port can self-adjust to implement the necessary crossover circuit if it is needed. MDI and Auto-MDI-X ports are used only with twisted pair cables, so there is no need for coaxial or fiber optic cables.

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 that apply.) a. The 5 GHz frequency has more channels than the 2.4 GHz frequency. b. The 5 GHz frequency supports longer ranges than the 2.4 GHz frequency. c. The 5 GHz frequency conflicts with fewer common household devices than the 2.4 GHz frequency. d. The 5 GHz frequency transmits at faster speeds than the 2.4 GHz frequency.

A, C, D. The 5 GHz frequency has 23 channels available in the United States, while 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.

Alice is attempting to deploy an IEEE 802.11b/g wireless LAN on the fifth floor of a 10-story office building that is surrounded on all sides by other office buildings, all of which seem to be running many wireless LANs. Scanning the 2.4 GHz band, she sees literally dozens of networks, spread across all of the available channels. As a result, her wireless devices have trouble connecting to their Access Point (AP), and when they do, they achieve only low speeds. Which of the following tasks should Alice perform to enable the wireless clients to connect to the network more reliably? (Choose two.) a. Upgrade all of the wireless network devices to IEEE 802.11n. b. Configure all of the network devices to use WPA2 encryption with AES. c. Configure the wireless devices to use the 5 GHz band. d. Configure the AP to suppress SSID broadcasts. e. Upgrade all of the network devices to the latest firmware.

A, C. Upgrading the devices to 802.11n will enable them to use the 5 GHz band and evade the traffic generated by the surrounding networks. Configuring the devices to use the 5 GHz band will provide many more channels to choose from and will avoid the interference from the surrounding 2.4 GHz networks. The type of encryption that a wireless network uses has no bearing on the ability of the devices to avoid the interference generated by surrounding networks. Suppressing SSID broadcasts will not help the devices to connect to the network. Upgrading the firmware on the devices is not likely to have any effect on the connection problems when they are the result of interference from other networks.

. Which of the following elements can be used to identify the devices in a particular VLAN? (Choose all that apply.) a. Hardware addresses b. IP addresses c. DNS names d. Switch port numbers

A, D. Every network device has a unique hardware address coded into its network interface adapter, and administrators can use these addresses to select the devices that will be part of a specific Virtual Local Area Network (VLAN). 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. IP addresses are layer 3 (network layer) constructs, so they do not apply to layer 2 (data link layer) devices like switches. 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.

Which of the following wireless networking technologies will never experience interference from a 2.4 GHz wireless telephone? (Choose all that apply.) a. IEEE 802.11a b. IEEE 802.11b c. IEEE 802.11g d. IEEE 802.11n e. IEEE 802.11ac f. IEEE 802.11ax

A, E. IEEE 802.11b, 802.11g, 802.11n, and 802.11ax networks can use the 2.4 GHz frequency band for their transmissions, which can experience interference from a wireless telephone using the same frequency. IEEE 802.11a and IEEE 802.11ac, however, use the 5 GHz band, which will not experience interference from a 2.4 GHz phone.

Which of the following statements is true about an Ethernet network that uses CSMA/CD? a. Collisions are a normal occurrence. b. Collisions never occur unless there is a network fault. c. Collisions cause data to be irretrievably lost. d. Collisions are the result of duplicate IP addresses.

A. Collisions are a normal occurrence on an Ethernet network; they occur when two nodes transmit at exactly the same time. There need not be a network fault for collisions to occur. When collisions occur, the nodes involved retransmit their packets so that no data is lost. Collisions are a phenomenon of data link layer protocols; they have nothing to do with IP addresses, which are network layer constructs.

An enterprise network has been designed with individual departmental switches because, in most cases, the devices in a specific department exchange network traffic with other devices in the same department. Each of the departmental switches is also connected to a host switch, which enables devices to communicate with other departments. Which of the following terms describes this switching architecture? a. Distributed switching b. Port forwarding c. Traffic shaping d. Neighbor discovery e. Flow control

A. Distributed switching describes a hierarchical switching architecture in which remote switches (departmental switches in this case) handle most of the network traffic, with a host switch used only for traffic between the remote locations. Port forwarding is a routing method that redirects traffic intended for one IP address and port number to another. Traffic shaping is a series of techniques that optimize the allocation of network bandwidth. Neighbor discovery is an IPv6 technique used to find addresses of devices and services on the local network. Flow control is a technique for regulating a system's transmission speed.

For the Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) mechanism to function properly on an Ethernet network, host systems must be able to detect when a collision occurs, so they can react to it. Which of the following cabling errors can prevent the collision detection process from functioning properly? a. Excessively long cable segments b. Incorrect wiring pinouts c. Too many systems on a single network d. An excessive number of collisions

A. For CSMA/CD to function properly, a system must detect a packet collision while it is transmitting the packet. If cable segments are too long, the packet might leave the transmitting system before the collision is detected, resulting in a late collision, which cannot be retransmitted. Incorrect pinouts, too many systems, and excessive collisions typically will not prevent the collision detection system from occurring.

Which of the following terms defines a wireless LAN transmission technique in which devices use multiple antennae to increase transmission speeds? a. MIMO b. TDMA c. PAN d. Ant+

A. Multiple Input, Multiple Output (MIMO) calls for the use of two or more antennae, enabling wireless devices to effectively multiplex signals, thereby increasing their transmission speeds. Time Division Multiple Access (TDMA) is a communication technique that splits a frequency into multiple time slots, enabling it to carry multiple data streams. A Personal Area Network (PAN) provides communication among devices associated with a single person, such as smartphones. Ant+ is a wireless protocol that is typically used to monitor data gathered by sensors, such as those in cardiac pacemakers.

Which of the following IEEE standards calls for the use of the Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA) Media Access Control (MAC) mechanism? a. 802.11ac b. 802.1X c. 802.3 d. All of the above

A. The IEEE 802.11ac standard, like all of the wireless LAN standards in the 802.11 working group, uses CSMA/CA for MAC. The 802.1X standard defines an authentication mechanism and does not require a MAC mechanism. The IEEE 802.3 (Ethernet) standard uses Carrier-Sense Multiple Access with Collision Detection (CSMA/CD).

On an IEEE 802.11b/g/n wireless network running at 2.4 GHz with multiple Access Points (APs), the traditional best practice is to use channels 1, 6, and 11, with no two adjacent APs configured to use the same channel. Which of the following is the real reason why this is a good plan? a. Channels 1, 6, and 11 are the only channels with frequencies that do not overlap. b. Channels 1, 6, and 11 have more bandwidth than the other channels. c. Channels 1, 6, and 11 have greater ranges than the other channels. d. Channels 1, 6, and 11 are the default settings on most wireless devices.

A. Wireless LAN regulations call for 22 MHz channels in the 2.4 GHz band that are spaced 5 MHz apart, which means that they overlap. Channels 1, 6, and 11 are the only three channels that are distant enough from each other not to overlap. Therefore, they do not interfere with each other. Channels 1, 6, and 11 do not differ from the other channels in their bandwidth or their transmission range. Each wireless device can be set to use only one channel. Therefore, channels 1, 6, and 11 cannot all be the default setting.

Which of the following statements about VLANs are true? (Choose all that apply.) a. All of the devices in a particular VLAN must be physically connected to the same switch. b. A VLAN creates a limited broadcast domain on a switched network. c. You must have VLANs on a switched network for communication between computers on different cable segments to occur. d. A router is required for communication between VLANs.

B, D. The computers in a single Virtual Local Area Network (VLAN) can be located anywhere on a switched network, irrespective of the switches' physical configuration. 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 the use of 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. Routing capabilities are often integrated into switches to enable communication between VLANs.

Which of the following wireless networking standards is capable of supporting speeds of 54 Mbps and is also backward compatible with IEEE 802.11b? a. IEEE 802.11a b. IEEE 802.11g c. IEEE 802.11n d. Bluetooth e. IEEE 802.11

B. IEEE 802.11g supports transmission speeds up to 54 Mbps, and it is backward compatible with 802.11b equipment. IEEE 802.11 cannot run at 54 Mbps, and while 802.11a can, it is not compatible with 802.11b. IEEE 802.11n cannot run at 54 Mbps, though it can run at faster speeds. Bluetooth is not compatible with any of the IEEE 802.11 standards.

When a packet collision between two systems occurs on an Ethernet network, Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) causes the two systems to stop transmitting and generate a jam signal. After sending the jam signal, why do the two systems wait for a randomized backoff interval before retransmitting their packets? a. They need time to reassemble the packets. b. To prevent another collision from occurring. c. They need to rebuffer the packet. d. To recalculate the packets' checksum values.

B. After transmitting their jam signals, the two systems wait for a randomized interval. This is to prevent them from retransmitting their packets at the same time, resulting in another collision. It is not necessary for the systems to reassemble, rebuffer, or recalculate checksums for their packets.

VLANs create the administrative boundaries on a switched network that are otherwise provided by which of the following devices? a. Hubs b. Routers c. Domains 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 Virtual Local Area Networks (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. Domains are logical groups of network devices defined by the Domain Name System (DNS). Their functions are not related to VLANs in any way. 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.

Which of the following is a protocol that identifies VLANs by inserting a 32-bit field in the Ethernet frame? a. IEEE 802.1P b. IEEE 802.1Q c. IEEE 802.1X d. IEEE 802.1AB e. IEEE 802.1AX

B. IEEE 802.1Q is a standard defining a mechanism (called Ethernet trunking by some manufacturers) that identifies the Virtual Local Area Network (VLAN) to which a packet belongs by inserting an extra 32-bit field into its Ethernet frame. IEEE 802.1P is a standard that defines a mechanism for implementing Quality of Service (QoS) at the data link layer by adding a 3-bit field into Ethernet frames. IEEE 802.1X is a standard defining an authentication mechanism called Port-based Network Access Control (PNAC). IEEE 802.1AB is a standard defining the Link Layer Discovery Protocol (LLDP). IEEE 802.1AX is a specification for the Link Aggregation Control Protocol (LACP), which is a mechanism for combining physical ports into a single logical channel.

Which of the following Power over Ethernet (PoE) specifications supplies power to devices using the spare wire pair on a 10Base-T or 100Base-TX twisted pair network? a. Alternative A b. Alternative B c. 4PPoE d. All of the above

B. The Alternative B PoE variant can use the spare wire pair in a 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 also capable of using the data wire pairs.

Which of the following IEEE wireless LAN standards uses the Direct Sequence Spread Spectrum (DSSS) signal modulation technique? a. 802.11a b. 802.11b c. 802.11g d. 802.11n e. 802.11ac

B. The IEEE 802.11b standard calls for DSSS signal modulation. All of the other standards listed call for Orthogonal Frequency-Division Multiplexing (OFDM) encoding.

How do wireless networking devices conforming to the IEEE 802.11n and 802.11ac standards achieve transmission speeds greater than 72.2 Mbps? a. By using direct sequence spread spectrum (DSSS) modulation b. By using multiple antennae to transmit several data streams simultaneously c. By using frequencies in the 5 GHz band d. By sacrificing transmission range for speed

B. The IEEE 802.11n and 802.11ac standards support a transmission technique called Multiple Input, Multiple Output (MIMO), which combines the bandwidth of multiple data streams to achieve greater throughput. IEEE 802.11n and 802.11ac do use the 5 GHz band, but this in itself does not yield greater transmission speeds. The specified standards do not call for the use of DSSS modulation, nor do they sacrifice range for speed. In fact, 802.11n and 802.11ac networks can achieve greater ranges than the previous technologies.

Which of the following is a network layer protocol that uses ICMPv6 messages to locate routers, DNS servers, and other nodes on an IPv6 network? a. BGP b. NDP c. OSPF d. PoE

B. The Neighbor Discovery Protocol (NDP) is a network layer protocol that defines five new Internet Control Message Protocol version 6 (ICMPv6) packet types, which enable IPv6 systems to locate resources on the network, such as routers and DNS servers, as well as autoconfigure and detect duplicate IPv6 addresses. Border Gateway Protocol (BGP) is an exterior gateway protocol that is designed to exchange routing information among autonomous systems. Open Shortest Path First (OSPF) is a link state routing protocol that enables routers to exchange routing table information. Power over Ethernet (PoE) is a general term for standards defining mechanisms for power delivery over Ethernet cables, along with data signals.

Which of the following protocols prevents network switching loops from occurring by shutting down redundant links until they are needed? a. RIP b. STP c. VLAN d. NAT e. ARP

B. The Spanning Tree Protocol (STP) prevents packets from endlessly looping from switch to switch due to redundant links. Creating redundant links is a good preventive against switch failure, but packets transmitted over multiple links can circulate from switch to switch infinitely. STP creates a database of switching links and shuts down the redundant ones until they are needed. Routing Information Protocol (RIP) propagates routing table information. A Virtual Local Area Network (VLAN) is an organizational tool that operates within switches by creating multiple broadcast domains. Network Address Translation (NAT) is a routing method that enables private networks to share registered IP addresses. Address Resolution Protocol (ARP) is a protocol that discovers a system's MAC address by broadcasting its IPv4 address.

Which of the following best explains how tagging the native Virtual Local Area Network (VLAN) traffic can improve in-band switch management security? a. By renaming the default VLAN b. By preventing double-tagged packets c. By encrypting in-band management traffic d. By moving in-band management traffic off the native VLAN

B. When in-band switch management traffic, such as that generated by a Secure Shell (SSH) connection to a switch, uses the native VLAN, it is untagged by default. This is because the native VLAN is at first the default VLAN1, which is not tagged by the 802.1q protocol, leaving it open to certain types of double-tagging attacks. When you tag the native VLAN traffic, it is rendered immune to double-tagging. The default VLAN cannot be renamed, and SSH traffic is already encrypted by the sending workstation. Changing the native VLAN does not move the management traffic off that VLAN, although many authorities advocate the creation of a separate VLAN dedicated to in-band management traffic.

Which of the following wireless LAN standards include the ability to use Multiple Input, Multiple Output (MIMO) antennae? (Choose all that apply.) a. IEEE 802.11a b. IEEE 802.11b/g c. IEEE 802.11n d. IEEE 802.11ac e. IEEE 802.11ax

C, D, E. The IEEE 802.11n, 802.11ac, and 802.11ax standards include MIMO, which enables them to effectively multiplex signals using multiple antennae. This capability was first introduced in the 802.11n standard, so the 802.11a and 802.11b/g standards do not support it.

Which of the following technologies would you be less likely to find on the average home or small office network? (Choose all that apply.) a. NAT b. DHCP c. 10GBase-T d. VLAN

C, D. Home and small office networks typically consist of a single subnet and require only a basic switch without the advanced Virtual Local Area Network (VLAN) capabilities that enable administrators to create separate subnets. Most home and small office networks have a Dynamic Host Configuration Protocol (DHCP) server that assigns IP addresses and other TCP/IP configuration settings to clients. The DHCP server can be integrated into a broadband router or another Internet access sharing solution. Most home and small office networks support Network Address Translation (NAT), enabling them to use private IP addresses and still access the Internet. 10GBase-T is the designation for UTP-based 10 Gigabit Ethernet, which is an advanced standard for network interface adapters often found in servers.

Which of the following could be a valid MAC address for a network interface adapter? a. 10.124.25.43 b. FF:FF:FF:FF:FF:FF c. 00:1A:6B:31:9A:4E d. 03:AE:16:3H:5B:11 e. fe80::89a5:9e4d:a9d0:9ed7

C. A Media Access Control (MAC) address is a 6-byte hexadecimal value, with the bytes separated by colons, as in 00:1A:6B:31:9A:4E. Option A, 10.124.25.43, is all decimals and uses periods; this is an IPv4 address. Option B, FF:FF:FF:FF:FF:FF, is a valid MAC address, but this value is reserved for use as a broadcast address. Option D, 03:AE:16:3H:5B:11, is not a valid hexadecimal address, which should contain only numerals and the letters A to F. Option E, fe80::89a5:9e4d:a9d0:9ed7, is too long for a MAC address; this is a valid IPv6 address.

Which of the following topologies enables wireless devices to access resources on a wired network? a. Ad hoc b. Star c. Infrastructure d. Bus

C. An infrastructure topology uses a Wireless Access Point (WAP) to connect wireless devices to a wired network. An ad hoc topology connects wireless devices to each other, without connecting to a wired network. The star and bus topologies do not support wireless devices.

Which of the following devices is used to physically connect computers in the same 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 Virtual Local Area Networks (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 physically 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 broadcast domain with huge amounts of traffic and many collisions. Hubs, therefore, do not connect the computers in a VLAN.

Each of the following Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) events occurs on an Ethernet network when two stations transmit simultaneously, although not in the order listed. Which of the following events occurs immediately after the collision? a. The two stations observe a random backoff interval. b. The two stations transmit a jam signal. c. The two stations stop transmitting. d. The two stations listen to see if the channel is idle. e. The two stations begin retransmitting their frames.

C. Stations on a CSMA/CD network first check the medium to see if it is idle. If they detect an idle medium, they begin transmitting. If two or more devices transmit at the same time, a collision occurs. Immediately after a collision occurs, the two stations involved stop transmitting. After that, they send out a jam signal. Then, the two stations back off for a random interval, and the transmission process begins again.

Which of the following is the fastest speed achievable by a wireless LAN using the currently ratified IEEE 802.11 standards? a. 54 Mbps b. 600 Mbps c. 1.3 Gbps d. 2.6 Gbps

C. The 802.11ac standard defines a wireless LAN running at a speed of up to 1.3 gigabits per second (Gbps). None of the other ratified 802.11 standards call for speeds beyond 600 megabits per second (Mbps). No currently ratified standard enables speeds of 2.6 Gbps.

Which of the following protocols is responsible for inserting the tags into frames that enable switches to forward them to the appropriate Virtual Local Area Network (VLAN)? a. IEEE 802.3x b. IEEE 802.1X c. IEEE 802.1q d. IEEE 802.11ac

C. The IEEE 802.1q protocol is responsible for VLAN tagging, a procedure that enables network switches to support VLANs. Through the insertion of VLAN identifier tags into frames, switches can determine which VLAN each packet is destined for and forward it to the correct ports. IEEE 802.3x is one of the standards for wired Ethernet networks. IEEE 802.1X is a standard that defines a Port-based Network Access Control (PNAC) mechanism used for authentication on wireless and other networks. IEEE 802.11ac is a standard defining the physical and data link layer protocols for wireless networks.

Which of the following protocols uses a form of flow control called the sliding window technique? a. UDP b. HTTP c. TCP d. DNS

C. The Transmission Control Protocol (TCP) protocol uses a flow control technique in which the receiving system creates a window of a specific size and allows the transmitting system to send packets until that window is full. When the window is full, the sender stops transmitting. The receiver then sends back an acknowledgment packet that specifies the next packet it expects to receive from the sender. The User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), and Domain Name System (DNS) do not use the sliding window technique or any other form of flow control.

Which of the following is a cellular communication technology that is virtually obsolete in the United States? a. GSM b. CDMA c. TDMA d. LTE

C. Time Division Multiple Access (TDMA) is a communication technique that splits a frequency into multiple time slots, enabling it to carry multiple data streams. Commonly used in 2G cellular systems, the major U.S. carriers no longer use it in their 3G systems. Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), and Long-Term Evolution (LTE) are alternative communications techniques that are currently used by the major U.S. cellular carriers.

Alice has a network that consists of three Virtual LANs (VLANs) defined on all of the network's switches. VLAN 10 is the Sales VLAN, VLAN 20 is the Marketing VLAN, and VLAN 30 is the Accounting VLAN. Users are reporting that they cannot communicate with anyone outside of their own VLANs. What is the problem, and what must Alice do? a. The problem is a faulty VLAN configuration on one of the switches. Alice needs to re-create the VLANs and configure each VLAN for routing. b. One of the VLANs is configured to filter all other VLAN traffic for security purposes. Alice needs to change the filter on this VLAN. c. VLANs are limited to data link layer communication only. To allow communication between VLANs, Alice must add a router or a layer 3 switch to the network and configure it to route traffic between the VLANs. d. The VLANs are using different data link layer protocols. VLANs must use the same data link layer protocol in order to communicate.

C. VLANs are data link layer Local Area Networks (LANs) defined within switches. Only devices (and users) connected to ports belonging to the same VLAN can communicate with each other until a layer 3 device, such as a router or a layer 3 switch, is added to the network. Re-creating and reconfiguring the VLANs will not correct this problem. Traffic filters are usually implemented on routers. VLANs do not have to use the same data link protocol.

Port security on an Ethernet switch is implemented through the use of which of the following methods? a. Blacklisted MAC addresses b. Whitelisted MAC addresses c. Port-by-port MAC address filtering d. Spoofed MAC addresses

C. When implemented in an Ethernet switch, port security uses port-by-port MAC address filtering to allow only one MAC address to access each switch port. Blacklisting blocks the MAC addresses on the list from using all of the ports on the switch. Whitelisting allows the listed MAC addresses to use any port on the switch. MAC address spoofing is a method for defeating port security, blacklists, or whitelists.

Which of the following best describes the process of whitelisting on a wireless network? a. Using an Access Control List (ACL) to specify the IP addresses that are permitted to access a wireless network b. Using port protection to specify the well-known port numbers of applications that users are permitted to run over a wireless network c. Using MAC filtering to create a list of devices that are permitted to access a wireless network d. Using an AAA server to create a list of users that are permitted to access a wireless network

C. Whitelisting is the process of using MAC filtering to specify the hardware addresses of devices that are permitted to access a wireless network. Blacklisting, by contrast, is making a list of addresses that are denied access to the network.

Ralph is planning a wireless LAN installation for a warehouse with two offices at either end of the building, approximately 300 feet apart. If he installs a single Access Point (AP) in the center of the warehouse, equidistant from the two offices, which of the following standards should he look for when purchasing hardware so that workstations in both offices will be able to connect to the network at the best possible speed? a. IEEE 802.11a b. IEEE 802.11g c. IEEE 802.11n d. IEEE 802.11ac

C. Wireless networks using equipment based on the IEEE 802.11n standard can span indoor distances of up to 175 feet at speeds up to 600 Mbps. An 802.11ac network can run at faster speeds—up to 1.3 Gbps—but it is limited to approximately 115-foot distances. Networks using 802.11g equipment can span 150 feet, but they run at only a maximum of 54 Mbps. An 802.11a network cannot span more than 75 feet, and it runs at no more than 54 Mbps.

Which of the following components are required for two computers to communicate using an IEEE 802.11 wireless LAN in an ad hoc topology? a. A router connected to the Internet b. A Wireless Access Point (WAP) c. An external antenna d. None of the above

D. An ad hoc topology describes wireless computers that communicate directly with each other, without the need for any hardware other than their wireless network adapters. The ad hoc topology therefore does not require a router, an Internet connection, an Access Point (AP), or a special antenna.

When designing a wireless LAN installation, which of the following are valid reasons to install a unidirectional antenna in an Access Point (AP), rather than an omnidirectional one? (Choose all that apply.) a. The AP will be located against an outside wall. b. There are many interior walls between the AP and the most distant workstation. c. A unidirectional antenna can be focused to a specific signal pattern width. d. All of the above

D. By placing a unidirectional antenna against an outside wall, you can limit network access to users inside the structure. Unidirectional antennae provide greater signal strength than omnidirectional antennae, enabling their signals to penetrate more interior walls. It is possible to focus a unidirectional antenna to a wider or narrower signal pattern.

Which of the following is an abnormal occurrence on an Ethernet network? a. Packet retransmissions b. Collision detection c. Jam signals d. Late collisions

D. Collisions are a normal occurrence on an Ethernet network, but late collisions are not normal. Late collisions occur when two packets collide after one or more finishes transmitting. Packet retransmissions, collision detection, and jam signals are all normal occurrences on an Ethernet network.

A switch with auto-medium-dependent interface crossover (MDI-X) ports eliminates the need for which of the following? a. 8P8C connectors b. Switch-to-switch connections c. Straight-through cables d. Crossover cables

D. Ethernet implementations, such as 100Base-TX, which use separate wire pairs for transmitting and receiving data, require a crossover circuit to ensure that the transmit pins on each end of a connection are wired to the receive pins at the other end. This crossover circuit can be implemented in a patch cable—called a crossover cable—or by a switch port. Switches with auto-medium-dependent interface crossover (MDI-X) ports can detect the need for a crossover circuit and implement it automatically in the port. This eliminates the need for crossover cables. Auto-medium-dependent interface crossover (MDI-X) ports do not eliminate the need for 8P8C connectors, connections between switches, or straight-through cables.

The jumbo frame capability is associated with which layer of the Open Systems Interconnection (OSI) model? a. Application b. Transport c. Network d. Data link

D. Ethernet uses jumbo frames at the data link layer to transfer large amounts of data more efficiently. Ethernet typically restricts frame size to 1500 bytes, but jumbo frames enable Ethernet systems to create frames up to 9000 bytes. Frames are protocol data units associated only with the data link layer, so they do not apply to the network, transport, or application layer.

Which of the following routing protocols has both interior and exterior designations, based on whether it is used for routing within an autonomous system or on the Internet? a. RIP b. OSPF c. EIGRP d. BGP

D. The Border Gateway Protocol (BGP) is a highly scalable protocol used for routing both on private autonomous systems, where it is known as the Internal Border Gateway Protocol (iBGP) and maintains full mesh communication among all of the routers, and on the Internet, where it is known as the External Border Gateway Protocol (eBGP). Routing Information Protocol (RIP), Open Shortest Path First (OSPF), and Enhanced Interior Gateway Routing Protocol (EIGRP) do not have interior and exterior designations.

What is the term for the technology implemented in the IEEE 802.11ac standard that enables a wireless device to transmit multiple frames to multiple clients simultaneously? a. MIMO b. Channel bonding c. CSMA/CA d. MU-MIMO

D. The Multiple Input, Multiple Output (MIMO) technology introduced in the IEEE 802.11n standard enables wireless devices to transmit and receive signals using multiple antennae simultaneously. The Multiuser MIMO (MU-MIMO) variant defined in the 802.11ac standard advances this technique by enabling wireless devices to transmit multiple frames to different users simultaneously, using multiple antennae. Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA) is a Media Access Control (MAC) mechanism used by all 802.11 networks. Channel bonding is a wireless networking technique that combines channels to increase bandwidth.

Which of the following best explains why networks using Voice over IP (VoIP) often have separate voice and data Virtual Local Area Networks (VLANs)? a. To prevent voice and data packet conflicts b. To encrypt voice traffic c. To encrypt data traffic d. To prioritize voice traffic

D. When transmitting voice traffic on a network along with data traffic, the voice traffic should have priority, to ensure the quality of the stream. Separating data and voice traffic on separate VLANs enables switches to assign voice traffic a higher priority by applying appropriate tags to the voice packets. Separate VLANs are not needed to prevent packet conflicts or to encrypt either voice or data packets.