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Local Area Network (LAN)

two or more computers that exchange data, confined to a small geographic area usually one building.

Reason organizations need networks

Sharing, Communication, Organization, Money

Most popular Lan

Wired-computers and other devices are wired together using copper-based twisted-pair cables RJ45 plugs on each end.

wireless access point (WAP)

acts as the central connecting device for the network, such as laptops, PDAs, tablet computers, micro computers

VLAN- Virtual LAN

is a group of host with a common set of requirements that communicate as if they were connected together in a normal fashion on one switch, regardless of their physical location.

Perimeter network

aka as demilitarized zone DMZ-Small network that is set up separately from a company's private LAN and the internet.

Back-to-back configuration

involves DMZ situated between two firewall devices, which could be black box appliances or Microsoft Internet Security.

3-leg perimeter configuration

the DMZ is usually attached to a seperate connection of the company firewall- 1 to company LAN -1 to the DMZ -1 to the Internet.

Network topology

defines the physical connection of hosts in a computer network.

Star topology

most common topology, each computer is individually wired to a central connecting device with twisted-pair cabling.

Mesh topology

every computer connects to every other computer; no central connecting device is needed

Ring Topology

each computer is connected to the network using a closed loop; done with coaxial cable. This is a pretty outdated concept

Token Ring

sends data logicaly in a ring fashion, Token Ring network are physically connected in a star fashion, but logically a ring.


a group of networking technologies that define how information is sent and received between network adapters, hubs, switches, and other devices.


is a group of bytes packaged by a network adapter for transimission across the network, these frames are created on Layer 2 of the OSI model.

IEEE Institute of Electrical and Electronics engineers 802.3

defines carrier sense multiple access with collision detection or CSMA/CD


10 Mbps - 10Base5 - Thick coaxial


100 Mbps - 100Base-TX, 100Base-T4, 100Base-FX = TP using 2 pairs, TP using 4 pairs, Fiber optic


1000 Mbps or 1Gbps - 10GBASE-T - TWISTED PAIR


1000 Mbps or 1Gbps - 1000BASE-X - FIBER OPTIC




an architecture that distributes applications between servers such as Windows Server 2008 and client computers such as Windows 7 or Windows Vista.

File server

stores files for computers to share

Print server

controls printers that can be connected directly to the server or are connected to the network.

Messaging Server

email servers, but also fax, instant messaging, collaborative, and other types of messaging servers.

CTI-based server

company's telephone system meets its computer system, PBXs, and VOIP

Peer-to-Peer (P2P)

means each computer has an equal ability to serve data and to access data, just like any other computer on the network.

OSI model

7 layers which house different protocols within one of several protocol suites, how data communicates occur on computer networks.

Layer 1 - Physical layer

physical and electrical medium for data transfer, includes but is not limited to cables, jacks, patch pannels, punch blocks, hubs, and MAUs. UOM=Bits

Layer 2 - Data Link Layer

establishes, maintains, and decides how transfer is accomplished over the physical layer. Think-MAC address UOM= Frames

Layer 3 - Network layer

dedicated to routing and switching information to different networks. UOM= Packets

Layer 4 - Transport Layer

This layer ensures error-free transmission between host through logical addressing. Inbound & outbound ports are controlled in this layer. Ports = transport layer.

Layer 5 - Session Layer

This layer governs the establishment, termination, synchronization of sessions within the OS over the network and between host. Think log on, log off

Layer 6 - Presentation Layer

This layer translates the data format from sender to receiver in the various OSes that may be used. Exp = code conversion, data compression, and file encryption.

Layer 7 - Application Layer

This layer is where message creation and packet creation begins.

Communications subnetwork

the guts of OSI model transmission, consisting of layers 1 thru 3. Physical, data, network

MAC - Media Access Control

is a unique identifier assigned to network adapters by the manufacturer, 6 octets, and written in hexadecimal.


how you get the MAC address in the command prompt

arp -a

command prompt that will show IP addresses and corresponding MAC addresses of remote computers.

Layer 2 switch

Resides on the data link layer, most common type of switch used on a LAN. Hardware based and use MAC address, but security is a concern.

Virtual Lan (VLAN)

Layer 2 switching allows VLAN to be implemented to segment the network,reduce collisions, organize the network, boost performance, and hopefully, increase security.


displays IP addresses

Difference between layer 2 & 3

Layer 3 switches forward packets like a router, used in busy environments, and layer 2 switches forward frames like an advanced bridge.

Upper layers of OSI model

layers 4-7, transport, session, presentation, and application, deals with protocols, compression, encryption, and session creation.

netstat -an

displays a list of all the connections to and from your computer in numeric format.

Port 80

HTTP= Hypertext Transfer Protocol

Port 21

FTP=File Transfer Protocol

Port 110

POP3=Post Office Protocol Version 3

Port 143

IMAP=Internet Access Message Protocol

netstat -a

shows in depth TCP and UDP connections

Twisted-pair cables

cable most commonly used, copper based cables, 8 wires grouped into 4 pairs, they are twisted to reduce crosstalk and interference.

Straight through cable

most common type of patch cable, used to connect a computer to the central connecting device like a switch, usually a 568B on each end.

Crossover cable

used to connect like devices to each other, computer to computer, or switch to switch. 568B on one side and 568A on the other

Fiber Optic cable

used in longer distance runs, high data rate transfer, transmits light instead of electricity over glass or plastic.

Single-Mode (SM)

optic cable with an optical fiber that is meant to carry a single ray of light, used in longer distance runs 10km to 80km

Multi-mode (MM)

optic cable w/ larger fiber core, carries multiple rays of light. used in shorter runs up to 600 meters.

Wireless access point (WAP)

this device acts as a router, firewall, and IP proxy, allows connectivity of various wireless devices such as laptops, PDAs, and tablets.

Wireless network adapters

allows connectivity between a desktop computer or laptop and the wireless access point.

Wireless repeater

used to extend the coverage of a wireless network extends the signal out further, usually placed on the perimeter of the wireless network


54 Mbps - 5 GHz


11 Mbps - 2 GHz


54 Mbps - 2.4GHz


600 Mbps - 5GHz and 2.4GHz


Internet Protocol version 4, is the most frequently used communications protocol and resides on the network layer of the OSI model, IP addresses consist of 4 numbers each between 0-255.

classful network architecture

What IPv4 classification system is known as class A,B,C,D,E

Class A - IP range 0-127

Class B - IP range 128-191

Class C - IP range 192-239

Class D

IP range 224-239

Class E

IP range 240-255, reserved for future use, but has giving way to IPv6 instead


Class D is used for multicasting transmitting data to multiple computers

IP conflict

occurs when two computers are configured with the same IP address.

Public IP address

are ones that are exposed to the internet; any computers on the Internet can potentially communicate with them.

Private IP address

are hidden from the Internet and any other networks. usually behind a IP proxy or firewall device

Automatic Private IP Addressing (APIPA)

type of private range that was developed by Microsoft for use on small peer-to-peer Windows networks. Uses class B, auto assigns IP addresses.

Default gateway

is the first IP address of the device that a client computer will look for when attempting to gain access outside the local network.

DNS server address

is the IP address of the device or server that resolves DNS address to IP address. This could be a Windows server or a all in one multifunction network device.


1 in binary


0 in binary


act of dividing a network into smaller logical subnetworks.

NAT- Network address translation

the process of modifying an IP address while it is in transit across a router, computer, or similar device, hides a person's private internal IP address.

PAT - Port address translation

a subset of NAT which translates both IP address and port numbers


is used to protect an organization's computers and switches on the LAN from possible attacks initiated by mischievous people on the Internet or other locations outside the LAN

Classless inter-domain routing (CIDR)

is a way of allocating IP addresses and routing Internet Protocol packets. EXP=, /16 means that the subnet mask has 16 masked bits (1s)


new generation of IP addressing for the Internet, can be used in small office networks and home networks. 128-bit 340 undecillion addresses.

Three types of IPv6

Unicast, Anycast, and Multicast

Unicast address

is a single address on a single interface.

Anycast address

assigned to a group of interfaces and are also most likely on separate host, but packets sent to such an address are delivered to all the interfaces in the group.

Multicast address

assigned to a group of interfaces and are also most likely on separate hosts

Global routing prefix

first three groups of numbers and it defines the network of the address

IPv6 subnet

This defines the individual subnet of the network that the address is located on.

Interface ID

This is the individual host IP portion. It can be assigned to one interface or more than one interface, depending on the type of IPv6 address.


abbreviated IPv6 address by removing unnecessary 0s


a tool that administrators can use to configure and monitor Windows computers from the command prompt.


verify connectivity to other computers.

IPv6 tunneling

IPv6 packets can be encapsulated inside IPv4 datagrams

Elevated Mode

running command prompt as an administrator is also known as


command displays information pertaining to your network adapter, namely TCP/IP configurations.


displays information pertaining to your network, TCP/IP configurations including your MAC address


command releases any IP configurations received from DHCP server


empties the DNS cache


displays NetBIOS over TCP/IP statistics for local and remote computers.


shows paths to a destination on another network


used to take control of a remote computer.


built in command line scripting utility that enables you to display and modify the network configurations of the local computer.


sends IP information to clients automatically making configuration of IP addresses on the network easier and automated.


Discovery, Offereing, Request, Acknowledge = DHCP sessions four step process


works on two ports 67 and 68

Terminal Services

also known as Remote desktop services is a type of thin-client terminal server it uses port 3389.

IPsec - Internet Protocol Security

protocol within the TCP/IP suite tat encrypts and authenticates IP packets.

SA - Security Association

Generates the encryption and authentication keys that are used by IPsec

AH - Authentication Header

provides connectionless integrity and the authentication of data

ESP - Encapsulating security payload

provides connectionless integrity and the authentication of data but also confidentiality when sending data

DNS - Domain Name System

Worldwide service that resolves host names to IP addresses, facilitates proper communication between computers

WINS - Windows Internet Name Service

resolves NetBios names to IP address

static route

one that has been manually entered into the routing table with the route add command.

dynamic route

one that has been implemented dynamically with special routing protocols.

RIP - Routing Info Protocol

dynamic protocol tat uses distance-vector routing algorithms to decipher which route to send data packets.

OSPF - Open Shortest Path First

link-state protocol that monitors the network for routers that have a change in their link state,meaning they were turned off, on and restarted, used in large networks

IGRP - Interior Gateway Routing Protocol

proprietary protocol used in large networks to overcome the limitations of RIP

BGP - Border Gateway Protocol

core routing protocol that bases routing decisions on the network path ad rules

Packet switching

how data packets are moved over switched wide area networks, such as X.25 and Frame Relay


communications protocol was one of the first implementations of packet switching.

PAD (packet assembler disassembler)

similar to a router which disassembles packets and sends them to a CSU/DSU which is like a modem for the LAN.


means that there is a clocking circuit that controls the timing of communications between the different routers.

Frame Relay

is the advancement of X.25 packet switching, designed for faster connections, packets are referred to as frames and it uses a virtual circuit.

T-carrier or telecommunications carrier system

is a cabling and interface implemented in mid-sized and large organizations that carry data at high speeds generally 1.544 MB or higher.


actual trunk carrier circuit that is brought into a company, a dedicated high-speed link or have other shared technologies running on top of it like Frame Relay and ISDN


Trunk carrier 3= 28 T1s, will come into a company as 224 wires or thereabouts and must be punched down to a DSX or like device.

ISDN - Integrated Services Digital Network

is a digital technology developed to combat the limitations of PSTN, sends data, fax, or talk on the phone simultaneously from one line.


Plain old telephone system


is standard for transmitting data on optical fiber cables at a rate of around 100 Mbps


worldwide system of connected computer networks, largest WAN in the world.

IETF - Internet Engineering Task Force

DNS is defined by


a private computer network or single Web site that an organization implements in order to share data with employees around the world.


extended to users outside a company and possible to entire organizations tat are separate from or lateral to the company

VPN - Virtual private network

a connection between two or more computers or devices that are not on the same private network.

PPTP - Point-to-point tunneling protocol

more common VPN (virtual private network) but is a less secure option.


a more secure VPN that is gaining in popular due to the inclusion of IPsec


primarily used to protect a network from malicious attacks and unwanted intrusions

Packet filtering

inspects each packet that passes through the firewall and accepts or rejects it based on a set of rules.

Stateless packet inspection SPI

aka pure packet filter, does not retain memory of packets that have passed through the firewall, more vulnerable to spoofing attacks

Stateful packet inspection

keeps track of the state of network connections by examining the header in each packet, is able to distinguish between legitimate and illegitimate packets.

NAT filtering

also known as the endpoint filtering, filters traffic according to ports TCP or UDP.

Application-level gateway - ALG

supports address and port translation and checks whether the type of application traffic is allowed.

Circuit-level gateway

works on the session layer of the OSI model when a TCP or UDP connection is established, and hides information about a private network, but they do not filter individual packet


port scanner, to scan for open ports on a computer

Back-to back configuration

a DMZ is situated between two firewall devices, which could be a black box appliance or Mircrosoft Internet Security and Acceleration Servers

DMZ or perimeter network

a small network that is set up separately from a company's private LAN and the Internet, allows users outside a company LAN to access specific services located on the DMZ

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