SYSTEM ADMINISTRATION AND MAINTENANCE NOTES PERIYAR UNIVERSITY

VG PRUCAS PENNAGARAM
Principles of Networking
 Networks are systems that are formed by links.
 People use different types of networks every day:
o Mail delivery system
o Telephone system
o Public transportation system
o Corporate computer network
o The Internet
 Computers can be linked by networks to share data and resources.
 A network can be as simple as two computers connected by a single cable or as complex as
hundreds of computers connected to devices that control the flow of information.
Computer Networks
 Network devices include:
o Desktop and laptop computers
o Printers and scanners
o PDAs and Smartphone’s
o File and print servers
 Resources shared across networks include:
o Services, such as printing or scanning
o Storage devices, such as hard drives or optical drives
o Applications, such as databases
 Different types of network media:
o Copper cabling
o Fiber-optic cabling
o Wireless connection
Benefits of Networking
 Fewer peripherals needed
 Increased communication capabilities
 Avoid file duplication and corruption
 Lower cost licensing
 Centralized administration
 Conserve resources
Types of Networks
A computer network is identified by: .
 The type of media used to connect the devices
 The type of networking devices used

 How the resources are managed
 How the network is organized
 How the data is stored
 The area it serves
Local Area Network (LAN)
 A group of interconnected computers that is under the same administrative control.
 Can be as small as a single local network installed in a home or small office.
 Can consist of interconnected local networks consisting of many hundreds of hosts, installed in
multiple buildings and locations.
Wide Area Network (WAN)
 A WAN connects LANs in geographically separated locations.
 A WAN covers a much larger area than a LAN.
 The Internet is a large WAN.
 Telecommunications service providers (TSP) are used to interconnect these LANs at different
locations.
Wireless LAN (WLAN)
 Wireless devices are used to transmit and receive data using radio waves.
 Wireless devices connect to access points within a specified area.
 Access points connect to the network using copper cabling.
 WLAN coverage can be limited to the area of a room, or can have greater range.
 You can share resources such as files and printers, and access the Internet on a WLAN.
Peer-to-Peer Networking
 Share files, send messages, and print to a shared printer.
 Each computer has similar capabilities and responsibilities.
 Each user decides which data and devices to share.
 No central point of control in the network.
 Best if there are ten or fewer computers.
 Disadvantages of Peer-to-Peer
o Without centralized network administration, it is difficult to determine who controls
network resources.
o Without centralized security, each computer must use separate security measures for
data protection.
o More complex and difficult to manage as the number of computers on the network
increases.
o Without centralized data storage, data backups must be performed by users.

Client/Server Network
 Client/server network model provides security and control for the network.
 Client requests information or services from the server.
 Server provides the requested information or service.
 Servers are maintained by network administrators.
o Data backups and security measures
o Control of user access to network resources
 Centralized storage and services include:
o Data stored on a centralized file server
o Shared printers managed by a print server
o Users have proper permissions to access data or printers
Networking Concepts and Technologies
 A computer technician is required to configure and troubleshoot computers on a network.
 A computer technician should understand IP addressing, protocols, and other network concepts.
Bandwidth
 amount of data that can be transmitted within a fixed time period
 measured in bits per second and is usually denoted by the following:
o bps -bits per second
o Kbps -kilobits per second
o Mbps -megabits per second
Three Modes of Transmission
Data is transmitted in one of three modes:
1. Simplex (Unidirectional transmission) is a single, one-way transmission. Example: The signal sent
from a TV station to your TV.
2. Half-duplex allows data to flow in one direction at a time. Simultaneous transmission in two
directions is not allowed. Example: Two-way radios, police or emergency mobile radios
3. Full-duplex allows data to flow in both directions at the same time.
 Bandwidth is measured in only one direction. 100 Mbps full-duplex means a bandwidth of 100
Mbps in each direction.
 Broadband technologies, such as digital subscriber line (DSL) and cable, operate in full-duplex
mode.
IP Address.
 An IP address is a unique number that is used to identify a network device.
 An IP address is represented as a 32-bit binary number, divided into four octets (groups of eight
bits): Example: 10111110.01100100.00000101.00110110 .

 An IP address is also represented in a dotted decimal format. Example: 190.100.5.54
 When a host is configured with an IP address, it is entered as a dotted decimal number, such as
192.168.1.5.
 Unique IP addresses on a network ensure that data can be sent to and received from the correct
network device.
IP Address Classes
 Class A:Large networks, implemented by large companies and some countries
 Class B: Medium-sized networks, implemented by universities
 Class C: Small networks, implemented by ISP for customer subscriptions
 Class D: Special use for multicasting
 Class E: Used for experimental testing
Subnet Masks
 Used to indicate the network portion of an IP address
 Is a dotted decimal number
 Usually, all hosts within a broadcast domain of a LAN (bounded by routers) use the same subnet
mask.
 The default subnet masks for three classes of IP addresses:
o 255.0.0.0 is the subnet mask for Class A
o 255.255.0.0 is the subnet mask for Class B
o 255.255.255.0 is the subnet mask for Class C
 If an organization owns one Class B network but needs to provide IP addresses for four LANs,
the organization will subdivide the Class B network into four smaller parts by using sub netting,
which is a logical division of a network. The subnet mask specifies how it is subdivided.
IP Address Configuration
 Manual configuration
o Manually configure each device with the proper IP address and subnet mask.
 Dynamic configuration
o A Dynamic Host Configuration Protocol (DHCP) server automatically assigns IP addresses
to network hosts.
 Network Interface Card (NIC) is the hardware that enables a computer to connect to a network
and it has two addresses:
o The IP address is a logical address that can be changed.
o The Media Access Control (MAC) address is "burned-in" or permanently programmed
into the NIC when manufactured. The MAC address cannot be changed.
Dynamic Host Configuration Protocol (DHCP)
 DHCP automatically provides computers with an IP address.

 The DHCP server can assign these to hosts:
o IP address
o Subnet mask
o Default gateway
o Domain Name System (DNS)
o server address
DHCP Process and Advantages
 DHCP process:
1. DHCP server receives a request from a host.
2. Server selects IP address information from a database.
3. Server offers the addresses to requesting host.
4. If the host accepts the offer, the server leases the IP address for a specific period of time.
 Advantages of DHCP:
o Simplifies the administration of a network
o Reduces the possibility of assigning duplicate or invalid addresses
Configure Host to Use DHCP
 Configure the host to "Obtain an IP address automatically" in the TCP/IP properties of the NIC
configuration window
Internet Protocols
 A protocol is a set of rules.
 Internet protocols are sets of rules governing communication within and between computers on
a network.
 Many protocols consist of a suite (or group) of protocols stacked in layers. These layers depend
on the operation of the other layers in the suite to function properly.
 The main functions of protocols:
o Identifying errors
o Compressing the data
o Deciding how data is to be sent
o Addressing data
o Deciding how to announce sent and received data
Common Network Protocols
 Protocols used for browsing the web, sending and receiving e-mail, and transferring data files

Internet Control Message Protocol (ICMP)
 Internet Control Message Protocol (ICMP) is used by devices on a network to send control and
error messages to computers and servers.
 PING (Packet Internet Groper) is a simple command line utility used to test connections between
computers
o Used to determine whether a specific IP address is accessible.
o Used with either the hostname or the IP address.
o Works by sending an ICMP echo request to a destination computer.
o Receiving device sends back an ICMP echo reply message.
Ping Command Switches
 ICMP echo requests (pings) are sent to the destination computer to determine the reliability and
reachability of the destination computer.
Physical Network Components
 Network devices:
o Computers
o Hubs
o Switches
o Routers
o Wireless access points
 Network media:
o Twisted-pair copper cabling

o Fiber-optic cabling
o Radio waves
Hubs
 Extend the range of a signal by receiving then regenerating it and sending it out all other ports
 Traffic is sent out all ports of the hub
 Allow a lot of collisions on the network segment and are often not a good solution
 Also called concentrators because they serve as a central connection point for a LAN
Bridges and Switches
 A packet, along with its MAC address information, is called a frame.
 LANs are often divided into sections called segments bounded by bridges.
 A bridge has the intelligence to determine if an incoming frame is to be sent to a different
segment, or dropped. A bridge has two ports.
 A switch (multiport bridge) has several ports and refers to a table of MAC addresses to
determine which port to use to forward the frame.
Routers
 Routers are devices that connect entire networks to each other.
o Use IP addresses to forward packets to other networks.
o Can be a computer with special network software installed.
o Can be a device built by network equipment manufacturers.
o Contain tables of IP addresses along with optimal routes to other networks.
Wireless Access Points
 Provide network access to wireless devices such as laptops and PDAs.
 Use radio waves to communicate with radios in computers, PDAs, and other wireless access
points.
 Have limited range of coverage.
Multipurpose Devices
 Perform more than one function.
 More convenient to purchase and configure just one device.
 Combines the functions of a switch, a router and a wireless access point into one device.
 The Linksys 300N is an example of a multipurpose device.
Twisted-Pair Cabling
 A pair of twisted wires forms a circuit that transmits data.

 The twisted wires provide protection against crosstalk (electrical noise) because of the
cancellation effect.
o Pairs of copper wires are encased in color-coded plastic insulation and twisted together.
o An outer jacket, called poly-vinyl chloride (PVC), protects the bundles of twisted pairs.
Two Basic Types of Twisted-PairCables
 Unshielded twisted-pair (UTP)
o Has two or four pairs of wires
o Relies on the cancellation effect for reduction of interference
o caused by electromagnetic interface (EMI) and radio frequency interference (RFI)
o Most commonly used cabling in networks
o Has a range of 328 ft (100 meters)
 Shielded twisted-pair (STP)
o Each pair is wrapped in metallic foil to better shield the wires from electrical noise and
then the four pairs of wires are then wrapped in an overall metallic braid or foil.
o Reduces electrical noise from within the cable.
o Reduces EMI and RFI from outside the cable.
Coaxial Cable
 A copper-cored network cable surrounded by a heavy shielding
 Types of coaxial cable:
o Thicknet or 10Base5 -Coax cable that was used in networks and operated at 10 megabits
per second with a maximum length of 500 m
o Thinnet or 10Base2 -Coax cable that was used in networks and operated at 10 megabits
per second with a maximum length of 185 m
o RG-59 -Most commonly used for cable television in the US
o RG-6 -Higher quality cable than RG-59 with more bandwidth and less susceptibility to
interference
Fiber-Optic Cable
 A glass or plastic strand that transmits information using light and is made up of one or more
optical fibers enclosed together in a sheath or jacket.
 Not affected by electromagnetic or radio frequency interference.
 Signals are clearer, can go farther, and have greater bandwidth than with copper cable.
 Usually more expensive than copper cabling and the connectors are more costly and harder to
assemble.
 Two types of glass fiber-optic cable:
o Multimode and Single-mode

LAN Topologies and Architectures
 Two Types of LAN Topologies
o Physical topology is the physical layout of the components on the network
o Logical topology determines how the hosts access the medium to communicate across
the network
LAN Physical Topologies
 A physical topology defines the way in which computers, printers, and other devices are
connected to a network.
o Bus
o Ring
o Star
o Hierarchical star
o Mesh
Bus Topology
 Each computer connects to a common cable
 Cable connects one computer to the next
 Ends of the cable have a terminator installed to prevent signal reflections and network errors
 Only one computer can transmit data at a time or frames will collide and be destroyed
 Bus topology is rarely used today. Possibly suitable for a home office or small business with few
hosts
Ring Topology
 Hosts are connected in a physical ring or circle.

 The ring has no beginning or end, so the cable does not need to be terminated.
 A special frame, a token, travels around the ring, stopping at each host.
 The advantage of a ring topology is that there are no collisions.
 There are two types of ring topologies:
o Single-ring and Dual-ring
Star Topology
 Has a central connection point: a hub, switch, or router
 Hosts connect directly to the central point with a cable
 Costs more to implement than the bus topology because more cable is used, and a central
device is needed
 Easy to troubleshoot, since each host is connected to the central device with its own wire.
Hierarchical or Extended Star Topology
 A star network with an additional networking device connected to the main networking device
to increase the size of the network.
 Used for larger networks
Mesh Topology
 Connects all devices to each other
 Failure of any cable will not affect the network
 Used in WANs that interconnect LANs
 Expensive and difficult to install because of the amount of cable needed
 The Internet is an example of a mesh topology
 Often used by governments when data must be available in the event of a partial network
failure
Logical Topologies
 The two most common types of logical topologies are broadcast and token passing.
 In a broadcast topology, there is no order that the hosts must follow to use the network – it is
first come, first served for transmitting data on the network.
 Token passing controls network access by passing an electronic token sequentially to each host.
When a host receives the token, it can send data on the network. If the host has no data to
send, it passes the token to the next host and the process repeats itself.
LAN Architecture
 Is the overall structure of a computer or communication system
 Designed for a specific use and have different speeds and capabilities.
 Describes both the physical and logical topologies used in a network.

 The three most common LAN architectures:
o Ethernet
o Token Ring
o Fiber-Distributed Data Interface (FDDI)
Ethernet
 Based on the IEEE 802.3 standard, which specifies that a network use the Carrier Sense Multiple
Access with the Collision Detection (CSMA/CD) access control method.
o Hosts access the network using the first come, first served broadcast topology method
to transmit data.
 Standard transfer rates
o 10 Mbps (Ethernet) “10Base-T”
o 100 Mbps (FastEthernet) “100Base-T”
o 1000 Mbps = 1 Gbps (Gigabit Ethernet) “1000Base-T”
Token Ring
 Reliable network architecture
 Originally developed by IBM
 Based on the token-passing access control method
 Often integrated with IBM mainframe systems
 Used with smaller computers and mainframes
 Physically, a star-wired ring because the outer appearance of the network design is a star
 Inside the device, wiring forms a circular data path, creating a logical ring
Fiber Distributed Data Interface (FDDI)
 A type of Token Ring network
 Often used for LANs, connecting several buildings in an office complex or on a university
campus
 Runs on fiber-optic cable
 High-speed performance combined with token-passing advantage
 Runs at 100 Mbps with a primary and secondary ring topology
 Normally, traffic flows only on the primary ring and uses a secondary ring is a backup.
 FDDI dual ring supports up to 500 computers per ring

Standards Organizations
Ethernet Standards
 Ethernet protocols describe the rules that control how communication occurs on an Ethernet
network.
o The 802.2 standard defines how a device addresses other devices on the medium.
o The 802.3 standard defines the methodology that devices must use when they use the
media.
o The 802.11x standards define how wireless devices communicate using radio waves.
Cabled Ethernet Standards
 IEEE 802.3 Ethernet standard specifies that a network implement the CSMA/CD access control
method.
 In CSMA/CD operation:
o All end stations "listen" to the network wire for clearance to send data.
o When the end station detects that no other host is transmitting, the
o end station will attempt to send data.

o If no other station sends any data at the same time, this transmission will arrive at the
destination computer successfully.
o If another end station transmits at the same time, a collision will occur on the network
media.
o The first station that detects the collision, sends out a jam signal to tell all stations to
stop transmitting and to run a backoff algorithm.
o All stations stop transmitting and re-try after a random period of time.
10BASE-T
 10BASE-T is an Ethernet technology that uses a star topology.
o The ten (10) represents a speed of 10 Mbps.
o BASE represents baseband transmission.
o The T represents twisted-pair cabling.
 Advantages of 10BASE-T:
o Installation is inexpensive compared to fiber-optic installation.
o Cables are thin, flexible, and easier to install than coaxial cabling.
o Equipment and cables are easy to upgrade.
 Disadvantages of 10BASE-T:
o The maximum length for a 10BASE-T segment is 328 ft (100 m).
o Cables are susceptible to Electromagnetic Interference (EMI).
100BASE-TX “FastEthernet”
 Has a theoretical bandwidth of 100 Mbps.
 The "X" indicates different types of copper and fiber-optic can be used.
 Advantages of 100BASE-TX:
o Transfer rates of 100BASE-TX are ten times that of 10BASE-T
o 100BASE-X uses twisted-pair, inexpensive and easy to install
 Disadvantages of 100BASE-TX:
o Maximum length for a 100BASE-TX segment is 329 ft (100 m).
o Cables are susceptible to Electromagnetic Interference (EMI).
1000BASE-TX “Gigabit Ethernet”
 Advantages of 1000BASE-T:
o 1 Gbps is ten times faster than Fast Ethernet and 100 times faster than Ethernet.
o Increased speed makes it possible to implement bandwidth-intensive applications, such
as live video.
o The 1000BASE-T architecture has interoperability with 10BASET and 100BASE-TX.
 Disadvantages of 1000BASE-T:
o Maximum length for a 1000BASE-T segment is 328 ft (100 m).
o It is susceptible to interference.

o Gigabit NICs and Switches are expensive.
o Additional equipment is required.
Wireless Ethernet Standards
 IEEE 802.11 is the standard that specifies connectivity for wireless networks.
 Wi-Fi (wireless fidelity), refers to the 802.11 family
o 802.11 (the original specification)
o 802.11b
o 802.11a
o 802.11g
o 802.11n
These protocols specify the frequencies, speeds, and other capabilities of the different Wi-Fi standards.
IEEE 802.11a WLAN Standard
 Allows data rates as high as 54 Mbps
 Devices operate in the 5 GHz radio frequency range
 Avoids some interference issues of 802.11b
 802.11a is not backward compatible to 802.11b
 Dual mode wireless NICs are available
 802.11a has a range of approximately 100 ft (30 m)
IEEE 802.11b WLAN Standard
 Operates in the 2.4 GHz frequency range
 Maximum theoretical data rate of 11 Mbps, but typically about 6.5 Mbps
 Average range of approximately 100 ft (30 m) at 11 Mbps and 295 ft (90 m) at 1 Mbps
 Range fluctuates depending on the operational speed.
 Signal quality dictates the operational speed of 802.11b.
 Bluetooth devices, cordless phones, and even microwave ovens operate in the 2.4 GHz band,
possibly causing interference.
IEEE 802.11g and 802.11n
 802.11g
o Allows data rates as high as 54 Mbps
o Operates in the same 2.4 GHz spectrum as 802.11b
o 802.11g is backward compatible with 802.11b
o Interoperability among all speeds (a, b, g) exists
o Average range of approximately 100 ft (30 m)
 802.11n
o Has a theoretical bandwidth of 540 Mbps

o Operates in either the 2.4 GHz or 5 GHz frequency range
o Maximum range of 164 ft (50 m)
o Expected approval for 802.11n is April 2008 or earlier
Wireless Ethernet Standards
OSI and TCP/IP Data Models
 Architectural model
o Separates functions of protocols into manageable layers
o Each layer performs a specific function in network communication
 TCP/IP model
o A four-layer model that explains the TCP/IP suite of protocols
o TCP/IP is the dominant standard for transporting data across networks
 Open Systems Interconnect (OSI) model
o Standards defining how devices communicate on a network
o Ensures interoperability between network devices
The TCP/IP Reference Model
 Frame of reference used to develop the Internet's protocols

 Consists of layers that perform functions necessary to prepare data for transmission over a
network
The OSI Model
 The OSI model is an industry standard framework that is used to divide network
communications into seven layers.
 Although other models exist, most network vendors today build their products using this
framework.
 A protocol stack is a system that implements protocol behavior using a series of layers.
o Protocol stacks can be implemented either in hardware or software, or in a combination
of both.
o Typically, only the lower layers are implemented in hardware, and the higher layers are
implemented in software.

Compare OSI and TCP/IP Models

Configuring a NIC and a Modem
 Install the NIC and the driver.
o If necessary, download an updated driver from the manufacturer.
 Connect the computer to the network.
 Also, you may need to install a modem to connect to the Internet.
Install or Update a NIC Driver
 Manufacturers publish new driver software for NICs
o May enhance the functionality of the NIC
o May be needed for operating system compatibility
 Install a new driver
o Disable virus protection software
o Install only one driver at a time
o Close all applications that are running so that they are not using any files associated
with the driver update.
o Visit the manufacturer's website and download a self-extracting executable driver file
that will automatically install or update the driver
Attach Computer to Existing Network
 Plug a network cable into the network port on the computer.
 Plug the other end into the network device or wall jack.
 After connecting the network cable, look at the LEDs, or link lights, next to the Ethernet port on
the NIC.
 If there is no activity, you may have to replace a faulty cable, a faulty hub port, or even a faulty
NIC to correct the problem.
Modem Installation
 A modem is an electronic device that transfers data between one computer and another using
analog signal over a telephone line.
 A transmitting modem converts digital data to analog signals, called modulation.
 The receiving modem reconverts the analog signals back to digital data, called demodulation.
 An internal modem plugs into an expansion slot on the motherboard and a software driver is
installed.
 External modems connect to a computer through the serial and USB ports and also require a
software driver.

Dial-up Networking (DUN)
 When computers use the public telephone system to communicate, it is called dial-up
networking (DUN).
 Modems communicate with each other using audio tone signals. DUN creates a Point-to-Point
Protocol (PPP) connection between two computers over a phone line.
 After the line connection has been established, a "handshaking sequence" takes place between
the two modems and the computers.
 The digital signals from the computers must be converted to an analog signal to travel across
telephone lines. They are converted back to the digital form, 1s and 0s, by the receiving modem
so that the receiving computer can process the data.
Establishing Connectivity
 Phone, cable, satellite, and private telecommunications companies provide Internet
connections.
 In the 1990s, low-speed modems used the plain old telephone system (POTS) to send and
receive data.
 Today, many businesses and home users have switched to high-speed Internet connections,
which allows for transmission of data, voice and video.
Integrated Services Digital Network (ISDN)
 A standard for sending voice, video, and data over telephone wires.
 Provides higher-quality voice and higher-speed data transfer than traditional analog telephone
service.
 Three services offered by ISDN digital connections: Basic Rate Interface (BRI), Primary Rate
Interface (PRI), and Broadband ISDN (BISDN).
 ISDN uses two different types of communications channels:
o "B" channel is used to carry the information -data, voice, or video.
o "D" channel is usually used for controlling and signaling, but can be used for data.

ISDN Types
Digital Subscriber Line (DSL)
 An "always-on" technology; there is no need to dial up each time to connect to the Internet.
 Uses the existing copper telephone lines to provide high-speed data communication between
end users and telephone companies.
 Asymmetric DSL (ADSL) is currently the most commonly used DSL technology.
o Has a fast downstream speed, typically 1.5 Mbps.
o Upload rate of ADSL is slower.
o Not the best solution for hosting a web server or FTP server.
DSL Types

Broadband Connectivity
 Broadband is a technique used to transmit and receive multiple signals using multiple
frequencies over one cable.
 Broadband uses a wide range of frequencies that may be further divided into channels.
 Some common broadband network connections include:
o Cable
o Digital Subscriber Line (DSL)
o Integrated Services Digital Network (ISDN)
o Satellite
Cable Modem
 A cable modem connects your computer to the cable company using the same coaxial cable that
connects to your cable television.
o You can connect the computer directly into the cable modem.
o You can connect a router, switch, hub, or multipurpose network device so multiple
computers can share the Internet connection.
DSL Modem and Filter
 Voice and data signals are carried on different frequencies on the copper telephone wires.
 A filter is used to prevent DSL signals from interfering with phone signals. Plug the filter into a
phone jack and plug the phone into the filter.

 The DSL modem does not need a filter. A DSL modem can connect directly to your computer, or
it can be connected to a networking device to share the Internet connection between multiple
computers.
A Typical ISDN Connection
 video, and data; therefore, it is considered a type of broadband.
 ISDN uses multiple channels and can carry voice,
Broadband Satellite
 Uses a satellite dish for two-way communication.
 Download speeds are typically up to 500 Kbps, while uploads are closer to 56 Kbps.
 People in rural areas often use satellite broadband because it is a faster connection than dial-up
and no other broadband connection may be available.
Preventive Maintenance for Networks
 Common preventive maintenance techniques should continually be performed for a network to
operate properly.
 Keep network rooms clean and change air filters often.
 Checking the various components of a network for wear.
 Check the condition of network cables because they are often moved, unplugged, and kicked.
 Label the cables to save troubleshooting time later. Refer towiring diagrams and always follow
your company's cable labeling guidelines.
 AC power adapters should be checked regularly.
 The uninterruptible power supply (UPS) should be tested to ensure that you have power in the
case of an outage.
Troubleshooting Process
Step 1 Gather data from the customer
Step 2 Verify the obvious issues
Step 3 Try quick solutions first
Step 4 Gather data from the computer
Step 5 Evaluate the problem and implement the solution
Step 6 Close with the customer
1. Gather Data from the Customer
 Customer information Company name, contact name, address, phone number

 Computer configuration Operating system, protection software, network environment,
connection type
 Use a work order to collect information
 Description of problem
 Open-ended questions
o What type of network connection is your computer using?
 Closed-ended questions
o Can you access the Internet?
2. Verify the Obvious Issues
 Examine the most obvious causes of a problem.
 Check that the network cables are properly connected.
 If a cable is not connected properly or if a NIC is improperly installed or configured, the LED link
lights on the NIC will not light.
 Check the wireless access point signal strength in your network client software.
 Use the ipconfig tool to make sure that the computer has a valid, unique IP address. Check for
errors in the subnet mask and default gateway address.
3. Try Quick Solutions First
 Check that all cables are connected to the proper locations.
 Unseat and then reconnect cables and connectors.
 Reboot the computer or network device.
 Login as a different user.
 Repair or re-enable the network connection.
 Contact the network administrator.
4. Gather Data from the Computer
 Ping is used to check network connectivity. It sends a packet to the specified address and waits
for a reply.
 Nslookup is used to query Internet domain name server. It returns a list of hosts in a domain or
the information for one host.
 Tracert is used to determine the route taken by packets when they travel across the network. It
shows where communications between your computer and another computer are having
difficulty.
 Net View is used to display a list of computers in a workgroup. It shows the available shared
resources on a network.
5. Evaluate Problem & Implement Solution
You may need to conduct further research

 Problem solving experience
 Other technicians
 Internet search and technical websites
 News groups and online forums
 Manufacturer FAQs
 Computer and device manuals
6. Close with the Customer
When you are confident that the problem is resolved:
 Document the customer information, problem description, and steps to resolve the issue in the
work order.
 Explain to the customer how you solved the problem .
 Let the customer verify that the problem has been solved.
 Complete all documentation including sales orders, time logs, and receipts.
 Complete the work order.
 Update the repair journal. You can use the notes from the journal for future reference.
Common Problems and Solutions

The Importance of Security
 Private information, company secrets, financial data, computer equipment, and items of
national security are placed at risk if proper security procedures are not followed.
 A technician’s primary responsibilities include data and network security.
Security Threats
Types of attacks to computer security:
 Physical
o Theft, damage, or destruction to computer equipment.
 Data
o Removal, corruption, denial of access, unauthorized access, or theft of information.
Potential threats to computer security:
 Internal threats
o Employees can cause a malicious threat or an accidentalthreat.
 External threats
o Outside users can attack in an unstructured or structured way.
Viruses, Worms, and Trojan Horses
 A computer virus is software code that is deliberately created by an attacker. Viruses may collect
sensitive information or may alter or destroy information.
 A worm is a self-replicating program that uses the network to duplicate its code to the hosts on
the network. At a minimum, worms consume bandwidth in a network.
 A Trojan horse is technically a worm and is named for its method of getting past computer
defenses by pretending to be something useful.
 Anti-virus software is designed to detect, disable, and remove viruses, worms, and Trojan horses
before they infect a computer.
Web Security
Attackers may use any of these tools to install a program on a computer.
 ActiveX Controls interactivity on web pages
 Java Allows applets to run within a browser
o Example: a calculator or a counter
 JavaScript Interacts with HTML source code to allow interactive web sites Example: a rotating
banner or a popup window
Adware, Spyware, and Grayware

 Typically installed without the user’s knowledge, these programs collect information stored on
the computer, change the computer configuration, or open extra windows on the computer and
all without the user’s consent.
Denial of Service (DoS)
 Denial of service (DoS) is a form of attack that prevents users from accessing normal services,
such as e-mail or a web server
 Sends enough requests to overload a resource or even stopping its operation
 Ping of Death is a series of repeated, larger than normal pings intended to crash the receiving
computer
 E-mail Bomb is a large quantity of bulk e-mail that overwhelms the e-mail server preventing
users from accessing e-mail
 Distributed DoS is an attack launched from many computers, called zombies
Spam and Popup Windows
 Spam is unsolicited email that can be used to send harmful links or deceptive content.
 Popups are windows that automatically open and are designed to capture your attention and
lead you to advertising sites.
Use anti-virus software, options in e-mail software, popupblockers, and common indications of
spam to combatthese.
Social Engineering
 A social engineer is a person who gains access to equipment or a network by tricking people into
providing the necessary information
 The following are some basic precautions to help protect against social engineering:
o Never give out a password
o Always ask for the ID of the unknown person
o Restrict access of unexpected visitors
o Escort all visitors through the facility
TCP/IP Attacks
TCP/IP is used to control all Internet communications.
 A SYN flood randomly opens TCP ports, tying up network equipment or a computer with a large
number of false requests, causing sessions to be denied to others.
 DoS attempts to make a computer resource unavailable to its intended users. 8 IT Essentials: PC
Harware and Software Companion Guide
 DDoS is a DoS attack that uses “zombies” to make tracing the origin of the attack difficult.
 Spoofing is a method of gaining access to resources on devices by pretending to be atrusted
computer.
 Man-in-the-middle intercepts or inserts false information in traffic between two hosts.

 Replay uses network sniffers to extract usernames and passwords to be used later togain
access.
 DNS poisoning changes the DNS records on a system to point to false servers where the data is
recorded.
Computer Disposal and Recycling
 Erase all hard drives, and then use a third-party tool to fully erase all data.
 The only way to fully ensure that data cannot be recovered from a hard drive is to carefully
shatter the platters with a hammer and safely dispose of the pieces.
 To destroy software media (floppy disks and CDs), use a shredding machine designed for
shredding these materials. Security is Strengthened in Layers
Security Procedures
Security Policy
Questions to answer in writing a local security policy:
 What assets require protection?
 What are the possible threats?
 What should be done in the event of a security breach?
Protecting Equipment
Since stealing the whole PC is the easiest way to steal data, physical computer equipment must be
secured.
 Control access to facilities
 Use cable locks
 Lock telecommunication rooms
 Use security screws
 Use security cages around equipment
 Label and install sensors on equipment

Protecting Data
Methods of securing data:
 Password protection
 Data encryption
 Port protection
 Data backups
 File system security
Preventive Maintenance Techniques
 Regular security updates are essential to meet the threat from attackers constantly searching
for new ways of breaching security. Software manufacturers have to regularly create and issue
new patches to fix flaws and vulnerabilities in products.
Update signature files for virus checkers and spyware.
 Threats to security from viruses and worms are always present. Attackers constantly look for
new ways to infiltrate computers and networks.
 Because new viruses are always being developed, security software must be continually
updated.
 This process can be performed automatically, but a technician should know how to manually
update any type of protection software and all customer application programs.
 To update a signature file, follow these steps:
o Step 1. Set the Windows restore point.
o Step 2. Open the antivirus or antispyware program.
o Step 3. Locate the update control button, and select it.
o Step 4. After the program is updated, use it to scan your computer.
o Step 5. When the scan is complete, check the report for viruses or other problems that
could not be treated, and delete them yourself.
o Step 6. Set the antivirus or antispyware program to automatically update and to run on
a scheduled basis.
Install operating system service packs and security patches.
 Manufacturers of operating systems and software applications may provide code updates called
patches that prevent a newly discovered virus or worm from making a successful attack

Troubleshooting Process
Step 1 Gather data from the customer
Step 2 Verify the obvious issues
Step 3 Try quick solutions first
Step 4 Gather data from the computer
Step 5 Evaluate the problem and implement the solution
Step 6 Close with the customer
1. Gather Data from the Customer
 Customer information
o Company name, contact name, address, phone number
 Computer configuration
o Protection software, OS, network environment, connection type
 Description of problem
o Open-ended questions
 What changes were made to the security settings?
o Closed-ended questions
 Are the protection software signature files up-to-date?
2. Verify the Obvious Issues
Examine the most obvious causes of a problem.
 A visual inspection can resolve some issues.
o Broken locks, signs of tampering, missing equipment

 Has an attacker accessed the equipment?
o Unfamiliar login address in login windows, unexplained entries in system security logs,
missing or additional patch cords
 Wireless network issues
o Changes in access point configuration, unexplained connections in the access point
status display
3. Try Quick Solutions First
 Check that all cables are connected to the proper locations
 Unseat and then reconnect cables and connectors
 Reboot the computer or network device
 Login as a different user
 Check that the anti-virus and spyware signature files are up to-date
 Scan computer with protection software
 Check computer for the latest OS patches and updates
 Disconnect from the network
 Change your password
4. Gather Data from the Computer
 Third-party software, such as anti-virus and antispyware applications, can report on the files
that have been infected.
 There are several tools available in the operating system that a technician can use:
o Verify that the signature file is current.
o Check the security software log file for entries.
o Task Manager is used to check for unknown applications that are running.
5. Evaluate Problem & Implement Solution
1 Evaluate the information gathered from the customer and from the laptop
2. Determine possible solutions
3. Implement the best solution
4. If a proposed solution doesn’t correct the problem, reset the computer back to the original state and
try another proposed solution.
NOTE: Never ask a customer to reveal a password.
6. Close with the Customer
 Discuss with customer the solution implemented.
 Have customer verify problem is solved.

 Provide all paperwork to customer.
 Document steps of solution in work order and in technician’s journal.
 Document components used in repair.
 Document time spent to resolve the problem.
Common Problems and Solutions

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