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LANs consist of more than just computers and cables, however. To attach a computer to the network, it must have a network interface card (NIC) in it, and to attach the cables to the NICs, they must have connectors on them. In addition, some network topologies require other hardware elements, such as hubs. More complicated network installations consist of multiple LANs connected using devices such as bridges, routers, switches, gateways, or even wide area network (WAN) links. You must understand the functions of all of these components and devices, and this objective domain tests your knowledge of them.
Tested Skills and Suggested Practices
The skills that you need to successfully master the Media and Topologies objective domain on the Network+ Certification exam include:
Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 2, "Network Hardware."
Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for "bus topology," "mesh topology," "ring topology," "star bus topology," "star topology," and "topology."
Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1, 2, 3, and 5 in Chapter 5, "Data-Link Layer Protocols."
Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for "Ethernet," "Fiber Distributed Data Interface," "Token Ring," and "wireless networking."
Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 5, "Data-Link Layer Protocols."
Spurgeon, Charles. "Quick Reference Guides to 10 Mbps Ethernet" and "Quick Reference Guides to 100 Mbps Ethernet." These documents are available on Charles Spurgeon's Web site at http://wwwhost.ots.utexas.edu/ethernet/ethernet-home.html.
Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1 in Chapter 2, "Network Hardware."
Connectivity Knowledge Platform. "Connector Reference Chart." This document is available on CKB's Web site at http://www.mouse.demon.nl/ckp/misc/conchart.htm.
Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 14, "Planning the Network."
Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for "cabling," "coaxial cabling," "fiber optic cabling," "twisted pair cabling," and "unshielded twisted pair (UTP) cabling."
Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1, 2, and 3 in Chapter 3, "Network Connections," Lesson 2 in Chapter 2, "Network Hardware," Lesson 5 in Chapter 5, "Data-Link Layer Protocols," and Lesson 2 in Chapter 12, "Remote Network Access."
University of Western Ontario. "Bridges vs. Switches vs. Routers." This comparison table is available on the UWO Web site at http://www.csd.uwo.ca/courses/CS457a/reports/handin/efteevan/A1/compare.html.
Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for "access point," "bridge," "Channel Service Unit/Data Service Unit (CSU/DSU)," "gateway," "hub," "Integrated Services Digital Network (ISDN)," "modem," "network interface card (NIC)," "router," "switch," and "wireless networking."
There are three main topologies associated with local area networking, and two others listed here that are seen less often.
A company with a 25-node Thin Ethernet network is planning to upgrade to Fast Ethernet using UTP cable. Which of the following topology changes must they make during the upgrade process?
A. Bus to ring
A. The bus topology is indeed used by Thin Ethernet networks. The ring topology is used by Token Ring and FDDI networks among others, but it is not used by any type of Ethernet network.
B. Ring to star
B. Thin Ethernet networks use coaxial cable, which can only be installed using the bus topology. The star topology is used by Fast Ethernet networks running over UTP cable, however.
C. Bus to star
C. The company's existing network uses Thin Ethernet, which consists of coaxial cable installed in a star topology. The new network uses Fast Ethernet, for which one of the physical layer options is UTP cable, which you always install using a star topology.
D. Mesh to ring
D. The mesh topology is not used by any form of Ethernet or LAN protocol because each computer would have to have a separate network interface for each of the other computers on the network. The ring topology is not used by any form of Ethernet network.
A maintenance worker accidentally cuts through a LAN cable while working inside an office's drop ceiling. On which type of topology is the cable break likely to cause the greatest disturbance in network communications?
A. When a cable break occurs on a bus network, the LAN is immediately split in two, preventing the computers on one side of the break from communicating with those on the other side. In addition, the break also creates two unterminated cable segments. This lack of termination will also affect the communications between computers on the same segment, effectively disrupting the entire network.
B. If a network uses a physical ring topology, a cable break would be catastrophic, preventing all communications from traversing the entire ring and from being removed from the ring by the transmitting system. This is why the ring topology is always implemented logically using the physical configuration of a star. When a cable break occurs, only the computer connected to the MAU by that cable is affected. The MAU detects the breakdown in communications with that computer and removes it from the logical ring.
C. On a star network, each computer is connected to the hub using a separate cable. A cable break therefore affects only one of the computer/hub connections. The rest of the computers can continue to communicate normally.
D. Hierarchical star
D. A hierarchical star network is similar to a regular star network in that a break in a cable connecting a computer to a hub affects only that computer. However, a break in a cable connecting two hubs is more serious. In this case, the cable break splits the network in two, preventing the computers on one hub from communicating with the computers on the other. Unlike a bus network, however, no termination is needed, so the communications between the computers connected to each hub proceed normally.
A and D
Which of the following statements about hubs and MAUs are true? (Choose two.)
A. Hubs amplify incoming signals before transmitting them.
A. A repeater is a device that amplifies signals so they can travel longer distances without suffering from signal degradation, also called attenuation. A hub's function is to transmit data received through any one of its ports out through all of its other ports. Hubs are also called multiport repeaters because they amplify the signals before retransmitting them.
B. Hubs provide termination for cable segments.
B. Networks using a star topology do not require termination, and hubs propagate signals to the network, not remove them.
C. MAUs are responsible for removing signals from the ring.
C. Signals are removed from the ring by the computer that originally transmitted them, not by the MAU.
D. MAUs maintain network integrity by removing malfunctioning nodes from the ring.
D. The primary reason for implementing the ring topology logically (inside the MAU) is to prevent a broken cable or malfunctioning computer from disrupting communications for the entire network. MAUs do this by performing an initialization process for each attached computer, which adds it to the ring. If a malfunction occurs, the MAU can remove the computer from the ring, bypassing it internally so that no data is transmitted to it or expected from it.
Which of the following LAN topologies is implemented logically and not physically?
A. The star topology gets its name from the use of a hub as the cabling nexus for all of the computers on the LAN. Even though the computers may not be dispersed evenly around a hub located in the exact center of the star, the physical layout of the network reflects the topology.
B. The bus topology consists of computers that are physically joined by cables running in a chain from one system to the next.
C. The mesh topology doesn't exist on a LAN, either logically or physically; it is an internetwork topology that provides redundant physical paths between destinations.
D. The ring topology is implemented logically by a MAU that transmits incoming data packets out through each one of its ports in turn, waiting for the connected computer to return the packet before proceeding to the next port. Physically, the network is cabled using a star topology.
|IEEE 802.3 (Ethernet)||CSMA/CD||10 Mbps
|Bus Star Star|
|IEEE 802.5 (Token Ring)||Token passing||4/16 Mbps||IBM Type 1/ UTP||Ring|
|FDDI||Token passing||100 Mbps||Fiber optic||Double ring|
|IEEE 802.11b||CSMA/CA||11 Mbps||DSSS||Ad hoc infrastructure|
Ethernet is the most popular data-link layer LAN protocol in the world, with millions of nodes installed. Ethernet networks can run at different speeds and use different cables and topologies, but the main identifying characteristic common to all Ethernet networks is the media access control (MAC) mechanism known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). A MAC mechanism regulates access to a network, ensuring that each computer has an opportunity to transmit its data. Each computer on a CSMA/CD Ethernet network begins the transmission process by listening to the network, and if it's free, proceeds to transmit its data. Sometimes two computers transmit simultaneously, however, causing a collision. Collisions are a normal occurrence on Ethernet networks because the protocol design enables the computers to detect them when they occur and compensate for them by retransmitting the data. Over its 25-year history, Ethernet has evolved considerably. It now supports a variety of physical layer options, including two types of coaxial cable running at 10 Mbps in a bus topology; UTP cable running at 10, 100, or 1,000 Mbps in a star topology; and fiber optic cable, also running at 10, 100, or 1,000 Mbps in a star topology.
Token Ring is a data-link layer protocol, developed by IBM and later standardized by the IEEE, that is fundamentally different than Ethernet. Token Ring networks all use a logical ring topology, although their physical configuration is that of a star. Token Ring's MAC mechanism is called token passing, and it is the reason for using of the ring topology. A special packet called a token circulates around the ring until a computer has data to transmit. This computer takes possession of the token and proceeds to transmit its data. Only the computer possessing the token can transmit, making it impossible for collisions to occur on a network that is functioning properly. After the data circulates around the ring, the transmitting system is responsible for removing it from the network and generating a new token. Token Ring networks originally ran at 4 Mbps and used a shielded twisted pair (STP) cabling system called IBM Type 1. Today, virtually all Token Ring installations run at 16 Mbps and use standard UTP cables.
FDDI is a 100 Mbps data-link layer protocol that was designed for network backbones that require high speeds and must span long distances. FDDI pre-dates Fast Ethernet (which has since largely replaced it), and at the time of its conception was the only 100 Mbps LAN protocol available commercially. FDDI uses the token passing MAC mechanism and the ring topology, much like Token Ring, except that in some cases, FDDI networks are physically cabled in a ring formation. The physical ring doesn't provide the fault tolerance of the logical ring, so the standard also defines the use of an optional double ring topology. In the double ring, traffic travels in opposite directions on the two rings and the computers are connected to both rings. If one ring gets broken, the other can still carry traffic to any destination on the network....
|Welcome to Network+ Certification|
|Objective Domain 1||Media and Topologies||1|
|Objective 1.1||Recognize the following logical or physical network topologies given a schematic diagram or description: star/hierarchical, bus, mesh, ring, wireless||5|
|Objective 1.2||Specify the main features of 802.2 (LLC), 802.3 (Ethernet), 802.5 (token ring), 802.11b (wireless), and FDDI networking technologies, including speed, access method, topology, media||11|
|Objective 1.3||Specify the characteristics (e.g., speed, length, topology, cable type, etc.) of the following: 802.3 (Ethernet) standards, 100BASE-T, 100BASE-TX, 10BASE2, 10BASE5, 100BASE-FX, Gigabit Ethernet||17|
|Objective 1.4||Recognize the following media connectors and/or describe their uses: RJ-11, RJ-45, AUI, BNC, ST, SC||25|
|Objective 1.5||Choose the appropriate media type and connectors to add a client to an existing network||31|
|Objective 1.6||Identify the purpose, features, and functions of the following network components: hubs, switches, bridges, routers, gateways, CSU/DSUs, network interface cards/ISDN adapters/system area network cards, wireless access points, modems||35|
|Objective Domain 2||Protocols and Standards||43|
|Objective 2.1||Given an example, identify a MAC address||53|
|Objective 2.2||Identify the seven layers of the OSI model and their functions||57|
|Objective 2.3||Differentiate between the following network protocols in terms of routing, addressing schemes, interoperability, and naming conventions: TCP/IP, IPX/SPX, NetBEUI, AppleTalk||63|
|Objective 2.4||Identify the OSI layers at which the following network components operate; hubs, switches, bridges, routers, network interface cards||69|
|Objective 2.5||Define the purpose, function and/or use of the following protocols within TCP/IP: IP, TCP, UDP, FTP, TFTP, SMTP, HTTP, HTTPS, POP3/IMAP4, TELNET, ICMP, ARP, NTP||73|
|Objective 2.6||Define the function of TCP/UDP ports. Identify well-known ports||81|
|Objective 2.7||Identify the purpose of the following network services (e.g., DHCP/BOOTP, DNS, NAT/ICS, WINS, and SNMP)||87|
|Objective 2.8||Identity IP addresses (IPv4, IPv6) and their default subnet masks||93|
|Objective 2.9||Identify the purpose of subnetting and default gateways||99|
|Objective 2.10||Identify the differences between public vs. private networks||103|
|Objective 2.11||Identify the basic characteristics (e.g., speed, capacity, media) of the following WAN technologies: packet switching vs. circuit switching, ISDN, FDDI, ATM, Frame Relay, SONET/SDH, T1/E1, T3/E3, OCx||107|
|Objective 2.12||Define the function of the following remote access protocols and services: RAS, PPP, PPTP, ICA||113|
|Objective 2.13||Identify the following security protocols and describe their purpose and function: IPsec, L2TP, SSL, Kerberos||117|
|Objective Domain 3||Network Implementation||121|
|Objective 3.1||Identify the basic capabilities (i.e., client support, interoperability, authentication, file and print services, application support, and security) of the following server operating systems: UNIX/Linux, NetWare, Windows, Macintosh||127|
|Objective 3.2||Identify the basic capabilities (i.e., client connectivity, local security mechanisms, and authentication) of the following clients: NetWare, UNIX/Linux, Windows, Macintosh||133|
|Objective 3.3||Identify the main characteristics of VLANs||137|
|Objective 3.4||Identify the main characteristics of network attached storage||141|
|Objective 3.5||Identify the purpose and characteristics of fault tolerance||147|
|Objective 3.6||Identify the purpose and characteristics of disaster recovery||153|
|Objective 3.7||Given a remote connectivity scenario (e.g., IP, IPX, dial-up, PPPoE, authentication, physical connectivity, etc.), configure the connection||159|
|Objective 3.8||Identify the purpose, benefits, and characteristics of using a firewall||165|
|Objective 3.9||Identify the purpose, benefits, and characteristics of using a proxy||171|
|Objective 3.10||Given a scenario, predict the impact of a particular security implementation on network functionality (e.g., blocking port numbers, encryption, etc.)||177|
|Objective 3.11||Given a network configuration, select the appropriate NIC and network configuration settings (DHCP, DNS, WINS, protocols, NetBIOS/host name, etc.)||181|
|Objective Domain 4||Network Support||187|
|Objective 4.1||Given a troubleshooting scenario, select the appropriate TCP/IP utility from among the following: Tracert, Ping, Arp, Netstat, Nbtstat, Ipconfig/Ifconfig, Winipcfg, Nslookup||193|
|Objective 4.2||Given a troubleshooting scenario involving a small office/home office network failure (e.g., xDSL, cable, home satellite, wireless, POTS), identify the cause of the failure||201|
|Objective 4.3||Given a troubleshooting scenario involving a remote connectivity program (e.g., authentication failure, protocol configuration, physical connectivity), identify the cause of the problem||207|
|Objective 4.4||Given specific parameters, configure a client to connect to the following servers: UNIX/Linux, NetWare, Windows, Macintosh||213|
|Objective 4.5||Given a wiring task, select the appropriate tool (e.g., wire crimper, media tester/certifier, punch down tool, tone generator, optical tester, etc.)||219|
|Objective 4.6||Given a network scenario, interpret visual indicators (e.g., link lights, collision lights, etc.) to determine the nature of the problem||225|
|Objective 4.7||Given output from a diagnostic utility (e.g., Tracert, Ping, Ipconfig, etc.), identify the utility and interpret the output||231|
|Objective 4.8||Given a scenario, predict the impact of modifying, adding, or removing network services (e.g., DHCP, DNS, WINS, etc.) on network resources and users||237|
|Objective 4.9||Given a network problem scenario, select an appropriate course of action based on a general troubleshooting strategy||243|
|Objective 4.10||Given a troubleshooting scenario involving a network with a particular physical topology (i.e., bus, star/hierarchical, mesh, ring, and wireless) and including a network diagram, identify the network area affected and the cause of the problem||249|
|Objective 4.11||Given a network troubleshooting scenario involving a client connectivity problem (e.g., incorrect protocol/client software/authentication configuration, or insufficient rights/permission), identify the cause of the problem||257|
|Objective 4.12||Given a network troubleshooting scenario involving a wiring/infrastructure problem, identify the cause of the problem (e.g., bad media, interference, network hardware)||263|