Network+ Exam Study and Preparation

 CompTIA Network+ Study Preparation

 

Network+ Outline (per CompTIA), broken down into 4 main areas, or “domains”:

ü      Domain 1.0 – Media & Topologies (20%)

ü      Domain 2.0 – Protocols & Standards (24%)

ü      Domain 3.0 – Network Implementation (23%)

ü      Domain 4.0 – Network Support (32%)

The above is based on the official (as of October, 2002) “Domains” put forth by CompTIA, found at:

http://www.comptia.com/certification/Network/objectives.asp

Note: The following is intended as a basic study guide for the CompTIA Network+ examination. It is NOT all-inclusive!

I make no guarantees, but feel free to use it as an accessory to your own studies. Putting this together helped me pass the examination, as it focused on my areas of weakness.  The “Domains” mentioned above include the official list of tested areas, and are far more inclusive than below. On the other hand, CompTIA only offers the outline form. There are no definitions, examples, or practice questions. I have briefly defined some of these items, with an emphasis on key words and, yes, brevity. Again, much is left out, and I emphasized areas of my own weaknesses.

 

Media & Topologies (brief/ key summaries)

v     Logical Topologies [1]

Ø      Star = All nodes connected to central point, i.e. a hub; if 1 system breaks, it doesn’t affect the whole scenario; lots of cabling required; if central point (hub)  fails, all become unusable; standard twisted-pair Ethernet uses this;

Ø      Bus = All nodes connected to same cable/bus, with 2 endpoints; 10Base2/10Base5 use Bus; no fault protection, however; requires termination;

Ø      Mesh = Every node has a connection to every other node. Very expensive; full redundancy, however; typical scenario for backbones;

Ø      Ring = All nodes connected in closed loop; broadcasts travel around the ring, each PC reads that which is addressed to it; spans long distances;

Ø      Wireless – WLAN; uses high-frequency radio waves to communicate between nodes;

Ø      Tree – hybrid; Star networks connect to each other via a central point;

v     Network Technologies

Ø      802.1 = Internetworking; network management;

Ø      802.2 = Data Link Layer; contains:

= LLC sub layer

= Media Access Control sub layer

Ø      802.3 = Ethernet (CSMA/CD)

Ø      802.4 = Token Bus LAN; tokens regulate traffic in bus schematic;

Ø      802.5 = Token Ring LAN; tokens regulate traffic in ring schematic; uses MAU;

Ø      802.6 = Metropolitan Area Network

Ø      802.7 = Broadband Technical Advisory

Ø      802.8 = Fiber

Ø      802.9 = Integrated Voice/Data

Ø      802.10 = Security

Ø      802.11 = Wireless; 802.11x specifies an “over-the-air interface” [2] between wireless clients/WAPS; 802.11b (“Wi-Fi”) = 11 Mbps in 2.4 GHz band; 802.11a = up to 45 Mbps in the 5 GHz band; uses “orthogonal frequency division multiplexing”; OFDM splits radio signals into smaller signals, which are then transmitted @ different frequencies to receiver [3] ;

Ø      802.12 = 100BaseVG-AnyLAN; uses demand priority; can use CAT3;

Ø      802.13 = not used

Ø      802.14 = Cable modem;

Ø      802.15 = Wireless Personal Area Network;

Ø      802.16 =  Broadband wireless access;

Ø      802.17 = Resilient packet ring;

v     Media types [4] (802.3) and some Connectors

Ø      10Base5 = Thicknet coaxial; 500 meter maximum; 100 systems/segment; uses AUI; used RG-8 coaxial cable and vampire taps to connect;

Ø      10Base2 = Thinnet coaxial; 185 meter maximum; 30 systems/segment; uses BNC and T-connectors; uses 50 ohm coaxial/RG-58 cable;

Ø      Another connector = “SC“, used in ATM; “ST” is used in patch panels and with fiber optic/coupling; Connector & Cabling Link, see footnote  [5] ;

Ø      10BaseT = Twisted pair; 100 meter maximum; 2 systems/ segment; [“T” = twisted pair];  cable is thinner/more flexible;

Ø      10BaseF =  Fiber optic cable; 2000 meter maximum; 1024 systems/ segment;

Ø      100BaseT_ (TX,T4, FX)= Fast Ethernet;  CSMA/CD; twisted pair cabling:

–         TX =  100 meter maximum length cable; uses CAT 5/Star topology; most popular of Fast Ethernet specifications; uses RJ-45 connectors;

–         T4 = 100 meter maximum cable; uses CAT3 b/c uses ALL 4 pairs of wires in cable;

–         FX =  2000 meter maximum; uses fiber;

 

Protocols and Standards
 

v     The ISO Network Model Standard

The International Standards Organization (ISO) put in place a standard: Open Systems Interconnection (OSI) network reference model. This is a seven layer architecture. Each layer takes responsibility for a different part of the architecture. The layers are arranged from the lower levels starting with the physical. A good way to remember the beginning letters, via silly expression: “Programmers do not throw sausage pizza away”. I must thank one of my CIS teachers at City College of San Francisco for this. Say it enough, it works. Some people prefer to memorize this upside down:

Ø      Physical Layer – The hardware itself. Recognizes bits only;

Ø      Data Link Layer = Data transfer method (802x ethernet). Puts data in frames;  ensures error-free data transmission. Divided into the following 2 sub layers:

– Logical Link control (LLC) = Keeps the link between two computers by establishing Service Access Points (SAPs): a series of interface points. 802.2.

– Media Access Control (MAC) = Coordinates the sending of data between computers. The 802.3, 4, 5, and 12 standards apply to this layer. The hardware address of NICs;

Ø      Network Layer = IP network protocol. Routes messages using the best path available (i.e. OSPF, RIP..)

Ø      Transport Layer = TCP, UDP. Ensures properly sequenced and error free transmission.

Ø      Session Layer = User interface to the network. Determines when the session is begun or opened, how long it is used, and when it is closed.

Ø      Presentation Layer = ASCII data syntax. Makes the type of data transparent to other layers; Used to translate and format data; It may include compression. It prepares the data, either for the network or the application depending on the direction it is going.

Ø      Application Layer = Provides services software applications needs. Provides the ability for user applications to interact with the network.

 

v     Network components defined and their location in the OSI [6]

Ø      Hubs = Multi-port repeaters; connects segments; located at OSI Physical layer;

Ø      Switches =  Filters and forwards packets between LAN segments; located at OSI Data Link layer/Network ;

Ø      Bridges = Isolate networks by MAC addresses; filter packets; translate protocols; located at OSI Data Link layer;

Ø      Routers =  connect LANs; connect nodes throughout an internetwork; located at OSI Network layer; protocol must match, i.e. IPX,  IP. (but not media type);

Ø      Brouters = Protocol-dependent devices; act as routers if protocol is recognized; act as bridges if not, then forward to next segment;

Ø      Gateways = translates each source layer protocol into the appropriate destination layer protocol; protocol conversion; located at OSI Transport layer/above;

Ø      CSU/DSU = Channel Service unit/Data Service unit; connects terminals to digital lines; used in T1 and T3 connections;

v         WAN Technologies in brief

Ø   Packet switching = TCP/IP/Internet; messages divided into packets; then they are individually sent, possibly via different routes; messages are reassembled at destination; perfect if slight delays are acceptable (unlike real-time data/streaming, etc.);

Ø  Circuit Switching =  POTS-based systems (i.e. telephone); real-time data uses this;

Ø  ISDN =  end-to-end digital connection; uses B (bearer) and D (data) channels; PRI vs. BRI (144 kbps vs. 1984 kbps);

Ø  FDDI = Fiber Distributed Data Interface; used for sending digital data over analog; often backbones use it; token-passing used;

Ø  ATM = Widely-used!; combines circuit/packet-switching; DSL is an example;

Ø  Frame Relay = Packet-switching protocol for WANs; T1/T3; bit slower than ATM;

Ø  Sonet/SDH = Synchronous Optical Network; defines standards for connecting fiber optic systems worldwide; SDH = International equivalent;

Ø  T1/E1 = data rates up to 1.54 Mbps; DSL; 24 64Kbit channels; E1 = European, 2 Mbps;

Ø  T3/E3 = data up to 43 Mbps; 672 64Kbps channels; E3 = European;

Ø  Ocx = Optical Carrier X:

OC =  Speed OC-1 =  51.85     Mbps OC-3 = 155.52   Mbps OC-12 = 622.08 Mbps OC-24 = 1.244  Gbps OC-48 = 2.488  Gbps OC-192=9.952  Gbps

 

Network Implementation

v             VLAN = 802.1q;  “a VLAN(virtual LAN) is a group of PCs, servers and other network resources that behave as if they were connected to a single, network segment even though they are not, physically” [7]

v             Fault Tolerance = Ability of a network to continue performing despite hardware/software failures; uses redundancy/mirroring in case of failures: mirrored servers, RAID disk storage, UPS;

v             Proxy = A middle point which sits between client (browsers frequently) and server; does caching of http addresses; performance and security device; will take care of requests if cached; filtering mechanisms as well (i.e. can stop certain outbound connections);

v             NAS =  Network-attached-storage; sole job usually = file sharing and storage; handles delivery of data only, as opposed to other typical server functions (i.e. web services, DNS, email, etc.); for example, a Snap Server [8] ;

 

Network Support

v         Tracert =  Route tracing; counts the number of hops a packet requires to reach a host; counts the time taken between hops;  good for troubleshooting slow connections on the internet;

v         Ipconfig = Windows command for determining IP information; also used for releasing/renewing IP addresses on a DHCP network in Windows 2000;

v         ARP = Address resolution protocol; used to convert IP addressing into hardware or physical ones; MAC address-related;

v         Troubleshooting a Network Problem (taken straight from Domain 4.9)

Ø     Establish the symptoms

Ø     Identify the affected area

Ø     Establish what has changed

Ø     Select the most probable cause

Ø     Implement a solution

Ø     Test the result

Ø     Recognize the potential effects of the solution

Ø     Document the solution



[1]   http://www.webopedia.com/Networks/Network_Topologies/

[2] http://www.webopedia.com/TERM/8/802_11.html

[3] http://www.webopedia.com/TERM/O/OFDM.html

[4] http://www.pctechtalk.com/forums/glossary.php?menu=15

[5] http://www.svisions.com/sv/f-ml-connect.html

[6] http://www.thelinuxreview.com/howto/intro_to_networking/c5434.htm

[7] http://www.networkmagazineindia.com/200205/primer.shtml

[8] http://www.snapserver.com

 

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