Local Area Networking

1
Local Area Networking

• Chapters 8, 9, and 16

2
Overview

• In this chapter, you will learn to
• Explain network technologies
• Explain network operating systems
• Install and configure wired networks
• Install and configure wireless networks
• Troubleshoot networks

3
Networking Technologies
4
The Big Questions

• How will each computer be identified?
• If two or more computers want to talk at the same
  time, how do you ensure all conversations are
  understood?
• What kind of wire should be used?
• How many wires in the cable? How thick? How long?
  What type of connectors?
• How can access to data be controlled?
• And the list goes on and on

5
A Few Basics

• A client machine requests information or services
• Network interface card (NIC) defines the client
• Breaks data into smaller data units (packets)
• A medium to connect the devices is needed
• Wired or wireless
• Operating system needs to be network aware
• A server provides information or services to the
  client

6
Topology

• Bus topology
• All computers connect to the network via a main
  line called a bus cable
• Ring topology
• All computers attach to a central ring of cable

7
Topology

• Star topology
• Computers on the networkconnect to a central
  wiring point (often a switch or a hub)
• Mesh topology
• Each computer has a dedicated line to
  everyother computer

8
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Packets/Frames and NICs
9
Packets, Frames, and NICs

• Data is broken up into small pieces and moved
  about the network
• Data moved in chunks called packets or frames
• Every network interface card (NIC) has a built-in
  identifier called a Media Access Control (MAC)
  address
• Designed to be unique
• Uses 48-bit long address
• Burned into a chip on the card

10
Packet Fields

• Packets contain the following fields
• MAC address of destination NIC
• MAC address of source NIC
• Data
• Data check or cyclic redundancy check
  (CRC) used to verify the datas
  integrity

11
Protocols

• Protocols are sets of rules
• May be used to define packet types, cabling and
  connectors, addresses, and much more
• A hardware protocol defines how to get data from
  one computer to another
• Ethernet is the dominant standard for todays
  networks
• Cables include coaxial, unshielded twisted pair,
  fiber optic
• Token Ring was developed by IBM but is losing
  popularity

12
Coaxial Ethernet

• Early Ethernet networks used coaxial cable (or
  just coax)
• Composed of a center cable surrounded by
  insulation, a shield of braided cable, and an
  outside protective cover
• A different type of coaxial cable is used by
  your VCRand TV

13
Thick Ethernet10Base5

• Thick Ethernet cable used
• RG-8 (Radio Grade) cable
• 10Base5
• 10 means data is transferred at 10 Mbps
• 5 means the maximum length of the cable is 500
  meters
• Uses a bus topology
• Computers are connectedone to another
• Every computer receives every packet of
  information

14
CSMA/CD

• Carrier sense multiple access/collision detection
  (CSMA/CD)
• To prevent collisions when there is multiple
  access to a cable
• Computers first do a carrier sense (listen to the
  cable for traffic) before trying to send data

15
CSMA/CD

• If two computers talk (try to send data) at the
  same time
• A collision results that corrupts the data
• Computers then decide when to resend the data

16
Reflection and Termination

• Signals traveling along a wire will bounce back
  when they get to the end
• This is called reflection
• Can corrupt signal
• A terminator absorbs the reflection

When an electrical signal reaches the end of a
wire
When an electrical signal reaches the end of a
terminated wire
Some of the signalis reflected back
There is no reflection
17
Connections

• Thicknet marked every 2.5 meters
• Devices are connected at these points
• Vampire connector pierces the cable
• It is also a transceiver that transmits and
  receives data, sometimes called an access unit
  interface (AUI) that connects to a Digital,
  Intel, or Xerox (DIX) connector
• Thicknet uses a bus topology
• Break in the cable takes down the whole network

18
Thicknet Connections
19
Thin Ethernet10Base2

• Thin Ethernet is also known as
  Thinnet
• Uses RG-58 coax
• Limited to 30 devices per segment
• Cable length limited to 185 meters
• Thinner and cheaper than Thicknet
• Transceiver built into NIC
• Uses twist-on BNC connectors
• Uses terminators

20
UTP Ethernet

• 10/100/1000BaseT (10xBaseT)
• Modern networks use UTP Ethernet
• 10BaseT runs at 10 Mbps
• 100BaseT runs at 100 Mbps
• 1000BaseT (Gigabit) runs at 1000 Mbps
• Uses a star bus topology
• Uses unshielded twisted pair (UTP) cabling

21
Star Bus Topology

• Most common topology used is a star bus
• All devices are connected to a central device
• Can be a hub or a switch
• Switch makes each port a separate network
• Limits collisions
• Helps bandwidth

22
Unshielded Twisted Pair

• UTP is predominant type of cabling used
• Pairs of wires are twisted together in an
  unshielded cable
• UTP cables come in categories (CATs) that define
  the maximum speed data can be transferred
• Called bandwidth
• CAT5, CAT5e, and CAT6 are most common today

CAT 1 Standard phone line CAT 2 ISDN T1 linesSpeeds up to 4 Mbps
CAT 3 Speeds up to 16 Mbps CAT 4 Speeds up to 20 Mbps
CAT 5 Speeds up to 100 Mbps CAT 5e Speeds up to 1 Gbps
CAT 6 Speeds up to 10 Gbps
23
Implementing 10xBaseT

• Requires at least two pairs of wires
• One for receiving and one for sending
• Cables use RJ-45 connectors
• RJ-11 for telephones
• The Telecommunications Industry Association/
  Electronics Industries Alliance (TIA/EIA) has two
  standards for connecting RJ-45 connectors
• TIA/EIA 568A and TIA/EIA 568B
• Use either but be consistent
• Wires are color-coded

1
8
24
Combo Cards

• Ethernet networks share same language
• Many NICs run at 10 or 100 Mbps
• Some NICs have BNCand RJ-45 ports
• Most NICs built into motherboards are
  autosensing
• Run at speed of network

25
Hubs and Switches

• Each PC is connected to a hub or switch in a
  10xBaseT network
• To add a device, simply run another cable to the
  hub or switch from the device
• The maximum separation between the device and the
  hub or switch is 100 meters
• Maximum of 1024 PCs per hub or switch
• Hubs act as repeaters that regenerate the signal
  before they send it back out to other ports
• Hubs come in 4, 8, 16, or 24 ports

26
Duplex and Half-Duplex

• Modern NICs can both send and receive data at the
  same time
• Called full duplex
• Older NICs could send and receive data but not at
  the same time
• Called half duplex
• Similar to a walkie-talkie

27
Fiber Optic Ethernet

• Uses light instead of electricity
• Immune to electrical interference
• Signals can travel up to 2000 meters
• Most Ethernet uses 62.5/125 multimode cable
• Uses two cables
• Uses SC (square-shaped) or ST (round) connectors
• Common standards
• 10BaseFL and 100BaseFL
• Usually reserved for data centers due to expense

28
Token Ring

• Developed by IBM
• Uses a star ring topology
• Incompatible with Ethernet
• Data travels in a ring
• Uses token passing
• A free token circulates the ring
• A device may send data only when it
  has the token

29
Implementing Token Ring

• Legacy Token Ring ran at 4 Mbps or 16 Mbps
  using IBM Type 1 cable
• Two-pair, shielded twisted pair (STP) cable
• Todays Token Ring networks may use UTP or STP
• STP comes in various types

30
Token Ring Connectors

• Token Ring cables use an IBM-type Data Connector
  (IDC)
• Universal Data Connectors (UDC) designed to plug
  into each other
• Uses a special hub called a multistation access
  unit (MSAU or MAU)

31
Other Connections

• Can connect two PCs together
• Parallel/serial
• Using crossover IEEE 1284 cable for parallel
  ports
• Use an RS-232 cable for serial ports
• FireWire
• Network aware
• Just connect
• USB
• Not quite as easy as FireWire but possible

32
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Network Operating System
33
Client/Server

• In a client/server environment, one machine is
  dedicated as a resource
• Shared over the network
• Uses a special network operating system (NOS)
• Optimized for sharing files and printers or other
  resources
• Protects access to the data or resources using
  security
• Called the server
• All other machines are clients or workstations
• Novell NetWare is an enterprise-level NOS

34
Peer-to-Peer

• In a peer-to-peer network, any machine on the
  network can act as client or server
• Peer-to-peer network operating systems include
• Windows 2000/XP
• Limited to 10 users accessing a file at one time
• Microsoft recommends no more than 15 PCs
• Useful for small networks only
• Limited security
• Also referred to as a workgroup

35
Peer-to-Peer

• User must log on to each individual computer
• Multiple computers, multiple logons

36
Domain-Based

• User logs onto domain controller
• One user, one logon
• Can access all computers (unless locked down
  with security)

37
Domain-Based

• Servers on the network may play one or several
  roles
• Domain controller (holds the security database)
• File server
• Print server
• Fax server
• Remote access services (RAS) server
• Application server
• Web server

38
Administrator Account

• Special user account that has complete and
  absolute power over entire system
• Password should be protected
• Joining a workgroup or becoming part of a domain
  is relatively easy
• Need Administrator access

39
Joining a Workgroup or Domain in Windows 98

• Joining a workgroup or becoming part of a domain
  is relatively easy
• Need Administrator access
• Select computer properties

40
Protocols

• Network protocol software
• Takes incoming data received by the network card
• Keeps it organized
• Sends it to the application that needs it
• Takes outgoing data from application and hands it
  over to the NIC to be sent out over the network
• The most common protocols used are
• NetBEUInonroutable, rarely used today
• IPX/SPXused by Novell
• TCP/IPused on Internet and most networks
• AppleTalkproprietary Apple protocol

41
Client and Server Software

• Client software
• Needed to access data and resources on a network
• Windows installs Client for Microsoft Networks
• Server software
• Any Windows PC may be turned into a server by
  enabling sharing of files, folders, and printers

42
Installing and Configuring a Wired Network
43
Network Connectivity

• To connect to a network you need
• Network interface card
• Physical hardware that connects the PC to the
  network wire
• Protocol
• The language the devices use to communicate
• Network client
• Allows the computer system to speak to the
  protocol
• To share resources, enable Microsofts File and
  Print Sharing

44
Installing a NIC

• When choosing a NIC, there are three requirements
• Must run at the proper speed (many NICs run at
  more than one speed)
• Must be for the proper technology
• Ethernet, Token Ring, fiber optic (FDDI)
• Must fit into your expansion slot
• PCI
• If NIC does not autoinstall, then use the Add
  Hardware Wizard in Control Panel

45
Configuring a Network Client

• You need a network client for each type of server
  NOS
• Client for Microsoft Networks
• Right-click My Network Places (or Network
  Neighborhood) and choose Properties
• Double-click the Local Area Connection icon (or
  choose Create a New Network Connection) and
  select Properties
• Client for Microsoft Networks is automatically
  installed when you install a NIC in Windows
• Client Service for NetWare
• Provides access to file and print services on
  NetWare servers

46
Client for Microsoft Networks
47
NetBEUI in Windows 2000

• NetBEUI
• Windows 2000 Start ? Settings ? Network and
  Dial-up Connections ? Double-click the Local Area
  Connection icon
• Click the Properties button
• Click Install button, highlight Protocols, and
  click Add ? NetBEUI
• Windows XP has dropped support for NetBEUI

48
NetBEUI

• NetBEUI
• Not routable (cant go through routers)
• Rarely used today

49
NWLink

• Microsofts implementation of IPX/SPX
• Youll also need to install Client Services for
  NetWare
• Install the same way you install NetBEUI but
  choose NWLink instead

50
Configuring TCP/IP

• TCP/IP is the most widely used protocol suite in
  networks today
• It is the protocol of choice for the Internet but
  is also used on private networks
• TCP/IP is installed just like NetBEUI and
  NWLinksimply choose Internet Protocol (TCP/IP)
• Youll need to configure an IP address and a
  subnet mask at the very least

51
IP Addressing

• IP addresses are unique on a network
• Expressed in dotted-decimal notation
• 202.34.16.11
• Composed of 32 bits in four octets
• 202 expressed as 1 1 0 0 1 0 1 0
• 34 expressed as 0 0 1 0 0 0 1 0
• 16 expressed as 0 0 0 0 1 0 0 0
• 11 expressed as 0 0 0 0 1 0 1 1

52
IP Addressing

• IP addresses are broken into classes based on the
  size of the network
• First number in dotted-decimal format determines
  class
• 15.16.17.18 15 is Class A
• 192.7.8.9 192 is Class C
• First number also determines subnet mask

Class Address Range Subnet Mask
Class A 1126 255.0.0.0
Class B 128191 255.255.0.0
Class C 192223 255.255.255.0
53
Classes of IP Addresses

• Some addresses are reserved
• 127.0.0.1 (the loopback address) is reserved for
  testing
• Three ranges are reserved for private networks
• 10.0.0.1 thru 10.255.255.255.254
• 172.16.0.1 thru 172.31.255.254
• 192.168.0.0 thru 192.168.255.254
• One range is reserved for Automatic Private IP
  Addressing
• 169.254.0.1 thru 169.254.255.254

54
Subnet Mask

• The subnet mask defines which portion of the IP
  address belongs to the network ID and which part
  belongs to the host ID
• Expressed as dotted-decimal format as 32-bit
  number starting with 1s and ending with 0s
• 1s represent a network-ID bit and 0s represent a
  host-ID bit
• For example, 11111111.00000000.00000000.0000000
  means that the first 8 bits define the network ID
  and the last 24 bits define the host ID
• The subnet mask is associated with an IP address

55
IP Addresses

• Two parts of an IP address
• Network ID represents the network or subnet
• Host ID represents the individual device
• You determine which is which with the subnet mask
• When the subnet mask is maximum, that portion of
  the IP address is the network ID
• 192.168.1.15 10.15.16.17 IP address
• 255.255.255.0 255.0.0.0 Subnet Mask
• 192.168.1.0 10.0.0.0 Network ID

56
TCP/IP Services

• TCP/IP is an entire suite of protocols that
  offers TCP/IP services such as
• Hypertext Transfer Protocol (HTTP) used on the
  World Wide Web
• Telnet used to access remote systems
• Ping to check communication
• TCP/IP is used to link multiple networks (local
  area networks or LANs) with other networks
• Forms a wide area network (WAN)
• Routers are used to route traffic among the LANs

57
Typical LAN

• Shows two networks or subnets
• Router is path to other network
• This router has two NICs (one on each network)
• Data sent from CPU1 to CPU2 goes through Default
  Gateway (different subnet)

Subnet 2 Network ID 192.168.15.0255.255.255.0
Subnet 1 Network ID 192.168.1.0255.255.255.0
CPU2
CPU1
Router
Default gateway
Default gateway
58
TCP/IP Settings

• Domain name service (DNS)
• To reach any host on a TCP/IP network, you need
  to know the IP address
• Instead of remembering IP addresses, you most
  likely simply remember a user-friendly name
• DNS resolves user-friendly names to actual IP
  addresses (name resolution)

59
Name Resolution

• Two types of names
• Internet (host) and Windows (NetBIOS)
• Seven types of name resolution
• Focus here only on DNS and WINS

Name Type Static Dynamic Cache
HostInternet name HOSTS file DNSserver Hosts cache View with IPConfig /DisplayDNS
NetBIOS Windows name LMHosts file WINSserver NetBIOS cache View with NBTSTAT C
Broadcast
60
TCP/IP Settings

• Windows Internet Name Service (WINS)
• Enables Windows network names to be resolved to
  IP addresses (like DNS does for Internet names)
• When configuring a NIC, you would define the IP
  address of the WINS server
• WINS is being used less and less

61
TCP/IP Settings

• IP address
• Subnet mask
• Default gateway
• The address of a machine (usually a router) that
  will deliver messages to hosts outside of your
  local segment or subnet

62
TCP/IP Settings DHCP

• Dynamic host configuration protocol
• Can manually configure TCP/IP settings
• Can configure to get TCP/IP settings
  automatically(from DHCP)
• Requires DHCP server
• On the client computer, simply
  choose Obtain an IP address
  Automatically

63
TCP/IP Tools Ping

• Ping
• Tests connectivity to a remote host
• Many options use ping /? for help

64
TCP/IP Tools IPCONFIG

• IPCONFIG
• Displays your TCP/IP settings in Windows
  NT/2000/XP
• Release and Renew allows you to get new TCP/IP
  information from a DHCP server

65
TCP/IP Tools NSLOOKUP

• NSLOOKUP
• Determines the name of a DNS server among other
  things
• Type exit to return to the command prompt

66
TCP/IP Tools TRACERT

• TRACERT
• Shows the route a packet takes to its destination

67
TCP/IP Tools APIPA

• Automatic Private IP Addressing (APIPA)
• If set to get addresses from DHCP but DHCP server
  cannot be reached, APIPA address is assigned
• Automatically assigns an IP address in range
  169.254.0.0 thru 169.254.255.254 with a subnet
  mask of 255.255.0.0
• No routing capabilities

DHCP cant be reachedAPIPA address assigned
DHCP
Router
CPU1
68
Sharing Drives and Folders

• To share a drive or folder, right-click it and
  select Sharing
• Share name is the name others will see on the
  network
• Windows 2000/XP uses NTFS-formatted drives
• Allows for much greater and precise control
• Set the network (Sharing tab) permissions to Full
  Control
• Then use NTFS permissions (Security tab) to
  exercise more precise control over who accesses
  the shared resource and how they access them

69
Sharing Drives and Folders

• Share Permissions
• Full Control
• Change
• Read
• NTFS Permissionsallow more control

70
Accessing Shared Resources

• Access shared drives or folders using My Network
  Places (Windows 2000/XP)
• You may also map a drive letter to a shared drive
  or folder
• Windows 2000 allows you to add a network icon
  instead of using a drive letter
• Windows XP adds a menu option

71
UNC

• Universal Naming Convention (UNC)
• Allows you to access network resources as follows
• Can enter directly from Run line to access UNC
  path

\\SERVER1\FREDC
Computer name
Share name
72
Sharing Printers

• To share a printer, just right-click on the
  printer and choose Sharing
• To access the printer
• Use the Add Printer icon
• Select Network Printer instead of Local Printer

73
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Installing and Configuring a Wireless Network
74
Introduction

• Wireless networks are growing in popularity
• Wireless networks use radio waves or beams of
  infrared light to communicate with each other
• Two primary types of wireless networks
• Based on IEEE 802.11 standard
• Based on Bluetooth technology

75
Wireless Networking Components

• Many capabilities built-in today
• Infrared ports standard in laptops, PDAs, and
  high-end printers
• Infrared not usually included in desktop PCs

76
Wireless Networking Components

• Wireless Ethernet and Bluetooth often integrated
  or can easily be added
• USB, PCI, PCI Express, or PC Card adapters

77
Wireless Networking Components

• Wireless access point (WAP)
• Acts like a hub to the wireless hosts in the area
• Bluetooth
• Built-in option on many newer PCs

78
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Wireless Networking Software
79
Wireless Networking Software

• Wireless devices use same networking clients and
  protocol as wired networks
• Use CSMA/CA (CA stands for collision avoidance)
• Another option is using Request to Send/Clear to
  Send (RTS/CTS)
• Sending node issues an RTS to the receiving node
  as a request
• Receiving node replies with a CTS when its clear
• Once data is received, receiving node sends an
  ACK (acknowledge)

80
Wireless Configuration Utility

• Wireless networking software is PnP
• Use a utility to configure parameters
• Windows built-in utility or vendor provided
• Configure the Service Set Identifier (SSID) here

81
Wireless Networking Modes

• Ad-hoc mode
• Each wireless node is in direct contact with
  every other node in a decentralized free-for-all
• Form an Independent BasicService Set (IBSS)
• Called peer-to-peer mode
• Good for a few computers or temporary network
  such as study groups or business meetings

82
Wireless Networking Modes

• Infrastructure Mode
• Use one or more WAPs to connect wireless nodes to
  a wired network segment
• A single WAP is called a Basic Service Set (BSS)
• Additional WAPs create an Extended Basic Service
  Set (EBSS)

83
Wireless Networking Security

• Three methods used to enhance security
• Service Set Identifier (SSID)
• Configure a unique SSID or network name
• Default is often name of vendor such as LinkSys
• Widely known so easy to guess
• Each node needs to have the same SSID
• Turn off SSID broadcasting
• MAC filtering
• Filtering based on each hosts MAC address
• Creates a type of accepted user
• Included in each packet, so can be discovered
  and impersonated

84
Wireless Networking Security

• Wireless Equivalency Privacy (WEP)
• Encrypts data using 40-bit or 104-bit encryption
• Provides authentication based on MAC addresses
• Significant flaws
• Wi-Fi Protected Access (WPA)
• Interim upgrade to WEP
• Uses encryption key integrity-checking
• WPA2 (IEEE 802.11i )
• Full upgrade to WEP
• Significant improvements
• Current wireless security standard

85
Speed and Range Issues

• Wireless speeds range from 2 Mbps to54 Mbps
• Speed affected by range
• Speed dynamically negotiated
• Maximum throughput at approximately 25 feet
• At edge of range, throughput may decrease to 1
  Mbps
• Range not exact
• Often listed as around 150 feet or 300 feet

86
Wireless Networking Standards

• 802.11-based wireless networking
• Three primary standards
• All can work in ad-hoc or infrastructure modes

802.11a 802.11b 802.11g
Maxthroughput 54 Mbps 11 Mbps 54 Mbps
Max range 150 feet 300 feet 300 feet
Frequency 5 GHz 2.4 Ghz 2.4 Ghz
Security SSID, MAC, WEP, WPA SSID, MAC, WEP, WPA SSID, MAC, WEP, WPA
Compatibility 802.11a 802.11b 802.11b, 802.11g
87
Wireless Networking Standards

• Infrared wireless networking
• Simple way to share data without adding any
  additional hardware or software
• Uses the Infrared Data Association (IrDA)
  protocol
• Line-of-sight required
• No authentication or encryption
• You cant be more than 1 meter away

Infrared (IrDA)
Max throughput Up to 4 Mbps
Max range 1 meter (39 inches)
Security None
Compatibility IrDA
Communication mode Point-to-point ad-hoc
88
Wireless Networking Standards

• Bluetooth
• Designed to create small wireless personal area
  networks (PANs)
• Typically used for peripherals
• Mice, keyboards, PDAs, etc.

Bluetooth High-powered Bluetooth
Max throughput 1 Mbps 2 Mbps
Max range 10 meters 300 feet
Compatibility Bluetooth Bluetooth
Communication mode PAN PAN
89
Wireless Networking Standards

• Cellular
• Many PDAs and phones today allow connection to
  Internet
• Downloads as quick as 400 to 700 Kbps
• Cellular networks have their own protocols
• Downside is the price

90
Configuring Wireless Networks

• Physically installing a wireless NIC is the same
  as installing a wired NIC
• Wireless network configuration utility
• Used to configure additionalparameters
• Configure SSID and encryption
• Configure communication mode
• Ad-hoc
• Infrastructure

91
Configuring Wireless Networks

• Wi-Fi
• Ad hoc
• Each wireless node needs to be configured with
  the same network name (SSID)
• May need to select a common channel
• Configure unique host IP addresses
• Configure File and Printer Sharing
• Infrastructure modes
• Requires a wireless access point (WAP)
• All nodes need to be configured with the same
  SSID
• Configure the WAP with clients that match the
  chosen options

92
Configuring Wireless Networks

• NETGEARwireless configurationutility

93
Configuring Wireless Networks

• Configuring a wireless access point is often done
  through a Web browser
• Enter the WAPs default IP address (see your
  documentation or try 192.168.1.1) in your browser
• Enter the default administrative password (in
  your documentation) to log in
• The next few slides show some screenshots of the
  configuration pages

94
Configuring Wireless Networks

• Sample home page

95
Configuring Wireless Networks

• Configuring MACaddress filtering

96
Configuring Wireless Networks

• Configuring encryption

97
Configuring Wireless Networks

• Infrared
• Not much to configure
• Confirm the IrDA protocol is installed
• To transfer files
• Use Wireless Link applet
• Use Windows Explorer
• To network two computers
• Choose Connect Directly to Another Computer

98
Configuring Wireless Networks

• Bluetooth
• Completely plug and play
• May need to use vendor-supplied drivers
• Bluetooth devices seek each other out
• Establish a master/slave relationship
• PANs sometimes have specialized software utility

99
Troubleshooting Networks
100
Troubleshooting Networks

• Networked and non-networked situations differ
  drastically
• Networked situations add complexity

If a user cant print from CPU1, it could be due
to many possible problems on the network.
X
Print server
X
X
Routeror switch
CPU1
X
X
X
Networked printer
X
101
Troubleshooting Networks

• Verify the symptom
• Talk with the user to try to get a precise
  description of the symptoms
• When did it happen?
• Does it happen during boot, when the OS loads, or
  after the system has been running for a while?
• What has changed?
• Try to find out if anything has changed
• Even recent changes before the problem began
  occurring

102
Troubleshooting Networks

• Check the environment
• Heat, humidity, dirt
• What OS? What applications? Do others use the
  computer?
• Reproduce the problem
• If a problem happens only once, its not a
  problem
• Otherwise, try to make the problem happen again
• Isolate the symptom
• Hardwareremove suspect parts
• Softwareremove background programs or boot into
  Safe Mode

103
Troubleshooting Networks

• Separate hardware from software
• Replace the suspect hardware with known good
  hardware
• Uninstall the suspect software and reinstall it
• Install the latest patch or upgrade
• Check for viruses
• Research
• Use search engines on the Internet
• Make the fix and test
• Keep track of what you did so you may return to
  the previous state if the fix does not work

104
OSI Seven-Layer Model

• Use as a guide in troubleshooting

Layer Number Name Description
Layer 1 Please Physical NICs (link light), cables, switches, hubs, etc. 1s, 0s
Layer 2 Do Data Link MAC addresses and CSMA/CD
Layer 3 Not Network IP operates here
Layer 4 Throw the Transport TCP/UDP operate here
Layer 5 Sausage Session Manages connections
Layer 6 Pizza Presentation Describes how to present data
Layer 7 Away Application Interacts with user
105
Mikes Four-Layer Model

• Hardware
• Check the hardware starting with the physical
  layer
• Protocols
• Is it installed and configured properly?
• Network
• Servers and nonservers
• Check users and groups and share names
• Shared resources
• Make sure the resource has been properly shared
• Check the access allowed