Chapter 09 - End of Chapter Review Questions

Review Questions 1. Which OSI layer is responsible for directing data from one LAN to another? a. Transport layer b. Network layer c. Data link layer d. Physical layer Answer: b. Network layer Explanation: Network layer protocols are responsible for directing data between LANs. Both LANs and WANs use the same protocols from OSI layers 3 and above, including the transport layer. LANs and WANs may differ at the physical and data link layers in access methods, topologies, and, sometimes, transmission media. 2. What kind of route is created when a network administrator configures a router to use a specific path between nodes? a. Trace route b. Static route c. Default route d. Dynamic route Answer: b. Static route Explanation: A network administrator configures static routes in a routing table to direct messages along specific paths between networks. A router automatically calculates the best path between two networks and accumulates these dynamic routes in its routing table. The default route in a routing table that the router will use if no other route is a match. Traceroute is a command-line utility. 3. When a router can’t determine a path to a message‘s destination, where does it send the message? a. Default gateway b. Routing table c. Administrative distance d. Gateway of last resort Answer: d. Gateway of last resort Explanation: The gateway of last resort is the router that accepts unroutable messages from other routers. The default gateway is the router where hosts send all routable messages. A routing table is a database that holds information about where hosts are located and the most efficient way to reach them. Each routing protocol is assigned a default AD (administrative distance), which is a number indicating the protocol’s reliability for that network. 4. A routing protocol’s reliability and priority are rated by what measurement? a. Routing table b. MTU c. Latency d. AD Answer: d. AD Explanation: Each routing protocol is assigned a default AD (administrative distance), which is a number indicating the protocol’s reliability for that network. A routing table is a database that holds information about where hosts are located and the most efficient way to reach them. MTU (maximum transmission unit) is the largest IP packet size in bytes allowed by routers in the path without fragmentation. Latency is the delay between the transmission of a signal and its receipt. 5. Which routing protocol does an edge router use to collect data to build its routing tables for paths across the Internet? a. RIPv2 b. BGP c. OSPF d. IP Answer: b. BGP Explanation: The only current EGP (exterior gateway protocol) is BGP (Border Gateway Protocol), which has been dubbed the “protocol of the Internet.” RIPv2 (Routing Information Protocol, version 2) and OSPF (Open Shortest Path First) are both interior gateway protocols. IP (Internet Protocol) is a core protocol in the TCP/IP suite that operates in the network layer of the OSI model and provides information about how and where data should be delivered. 6. What is the lowest layer of the OSI model at which LANs and WANs support the same protocols? a. Layer 2 b. Layer 3 c. Layer 4 d. Layer 5 Answer: b. Layer 3 Explanation: Both LANs and WANs use the same protocols from OSI layers 3 and above. LANs and WANs may differ at the physical and data link layers in access methods, topologies, and, sometimes, transmission media. 7. What kind of device can monitor a connection at the demarc but cannot interpret data? a. Line driver b. CSU/DSU c. DTE d. Smartjack Answer: d. Smartjack Explanation: A more intelligent version of an NIU (network interface unit) is a smartjack, or INID (Intelligent NID), which can provide diagnostic information about the interface. Essentially a repeater, a line driver can be installed either on copper lines or fiber lines to boost the signal across greater distances. The CSU/DSU (channel service unit/data service unit) serves as the endpoint for a dedicated connection between an ISP and a customer. The customer’s endpoint device on a WAN is called the DTE (data terminal equipment). 8. What specifications define the standards for cable broadband? a. PSTN b. HFC c. FTTC d. DOCSIS Answer: d. DOCSIS Explanation: Cable broadband was standardized by an international, cooperative effort orchestrated by CableLabs that yielded a suite of specifications called DOCSIS (Data Over Cable Service Interface Specifications). DSL (digital subscriber line) operates over the PSTN (public switched telephone network), also called POTS (plain old telephone service), which is a network of lines and carrier equipment that provide landline telephone service to homes and businesses. HFC (hybrid fiber coaxial) networks use fiber-optic cabling to connect the cable company’s distribution center, or headend, to distribution hubs and then to optical nodes near customers. Either fiber-optic or coaxial cable then connects a node to each customer’s business or residence via a connection known as a cable drop. FTTC (fiber-to-thecurb) is a service where the ISP runs a fiber connection to a nearby pole or equipment cabinet that serves a few customers. 9. What method does a GSM network use to separate data on a channel? a. SIM b. CDMA c. TDMA d. TDM Answer: c. TDMA Explanation: Digital communication of data on GSM (Global System for Mobile Communications) systems is separated by timeslots on a channel using TDMA (time division multiple access), which is similar to TDM (time division multiplexing). The primary difference is that multiplexed TDM signals all come from the same source (such as a router), while multiplexed TDMA signals come from several sources (such as several smartphones in the same vicinity). GSM networks require that a cellular device have a SIM (Subscriber Identity Module) card containing a microchip to hold data about the subscription a user has with the cellular carrier. CDMA (Code Division Multiple Access) differs from GSM in that it spreads a signal over a wider bandwidth so that multiple users occupy the same channel, a technology called spread-spectrum. 10. Which of these cellular technologies offers the fastest speeds? a. 4G-LTE b. LTE-A c. CDMA d. GSM Answer: b. LTE-A Explanation: LTE-A (LTE-Advanced) can realistically approach 4G standards. Sometimes misleadingly called 5G E (5G Evolution), LTE-A is basically true 4G as defined back in 2008 but only recently emerging in real-world networks. LTE (Long-Term Evolution) is an ambiguous marketing term that meant “faster than 3G but not really 4G.” CDMA (Code Division Multiple Access) and GSM (Global System for Mobile Communications) are both originally 2G technologies used by 3G for digital transmissions. 11. Where is an MPLS label inserted into a message’s headers? Answer: MPLS labels together are sometimes called a shim because of their placement between layer 2 and layer 3 information. For this reason, MPLS is sometimes said to belong to “layer 2.5.” 12. What four functions do all routers perform? Answer: 1. Connect dissimilar networks. 2. Interpret Layers 3 and 4 addressing and other information. 3. Determine the best path for data to follow. 4. Reroute traffic if a primary path is down but another path is available. 13. What database does a router consult before determining the most efficient path for delivering a message? Answer: Its routing table 14. Give three examples of routing metrics used by routers to determine the best of various available routing paths. Answer: (Any three) Hop count, theoretical bandwidth, actual throughput, path latency (or delay), path load, MTU, cost, reliability, network topology 15. List three IGPs (interior gateway protocols). Answer: (Any three) RIP, RIPv2, OSPF, IS-IS, EIGRP 16. How can you create a private and secure connection with your cloud network over the Internet? Answer: A VPN travels over an Internet connection to give direct and secure access to cloud resources. 17. List three transport methods that can be used to support an SD-WAN. Answer: Any three WAN connectivity methods, such as DSL, cable broadband, fiber broadband, leased line, MPLS, cellular, and satellite. 18. When you list a router’s routing table, one of the routes is labeled with an S. Which routing protocol was used to create this route? Answer: None—it’s a static route configured by a network administrator. 19. What command will ensure the configuration changes you made to a switch will persist after you restart the switch? Answer: copy running-config startup-config or copy run start 20. What device must be installed on a DSL network to protect the sound quality of phone calls? Answer: A splitter