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Network Support Group (Rajasthan)Network Support Group (Rajasthan)
Saturday, September 27 2008Saturday, September 27 2008
Welcome to 3i Infotech
“3i Infotech is an agile and fast growing global organization that drives customer success through innovative and flexible IT
solutions.
Large enough to depend on. Agile enough to perform”
Brief about 3i Infotech
• Founded in 1999. Revenue run rate of US$ 750m• Global provider of entire value chain solutions, in the area of
Banking, Financial Services and Insurance Capital Markets Mutual funds Enterprise Resource Planning and Management Government Software Services and IT Outsourcing BPO Services
• Powered by a multicultural team of 5000 technical and functional specialists• Physical presence in 11 countries• 500 customers in over 50 countries across 5 continents• Listed on NSE and BSE in India
Log on to www.3i-infotech.com for more details
• Maintain a formal dress code
• Always keep a smiling face
• Gents, come with clean shaven beard and shoes neatly polished
Your appearance
• Pick up the phone within three rings.
• Greet the user appropriately
• Understand the problem that the customer has logged
in at the help desk
• Treat each call /caller as ‘Important’
• Be courteous while talking to the customer on phone.
• Try to analyze and provide a solution if the problem is
simple, over phone.
Telephone etiquette
Introduction to OSI ModelIntroduction to OSI Model
Introduction to OSI Layer Introduction to OSI Layer When computers were first linked together into networks, moving information between different types of computers was a very difficult task.
In the early 1980s, the International Standards Organization (ISO) recognized the need for a standard network model. This would help vendors to create interpretable network devices. The Open Systems Interconnection (OSI) reference model, released in 1984, to addressed these needs. It divides the different functions and services provided by network hardware and software in 7 layers. This facilitates modular engineering, simplifies teaching and learning network technologies, helps to isolate problems and allows vendors to focus on just the layer(s) in which their hardware or software is implemented and be able to create products that are compatible, standardized and interoperable.
Introduction to OSI Layer Introduction to OSI Layer
The diagram below shows the 7 layers of the OSI Model, to remember them in the correct order a common mnemonic is often used: All People Seem To Need Data Processing
Introduction to OSI Layer Introduction to OSI Layer The Application, Presentation and Session layer are known as
the Upper Layer and are implemented in software.
The Transport and Network layer are mainly concerned with protocols for delivery and routing of packets to a destination and are implemented in software as well.
The Data Link is implemented in hard- and software and the Physical layer is implemented in hardware only, hence its name.
ApplicationApplication The Application layer provides network services
directly to the user's application such as a web browser, email software and Windows Explorer. This layer is said to be "closest to the user".Protocols that operate on this layer include: TELNET, HTTP, FTP, TFTP, SMTP, NTP, SNMP,
PresentationPresentation
This layer 'represents' the data in a particular format to the Application layer (masks the difference of data format between two dissimilar systems). It also defines encryption, compression, conversion and other coding functions.Specifications defined at this layer include: GIF, TIFF, JPEG, MPEG, MIME, and ASCII.
SessionSession
Establishes, maintains and terminates end-to-end connections (sessions) between two applications on two network nodes. It controls the dialogue between the source and destination node, which node can send when and how long. Also provides error reporting for the Application, Presentation and Session layer.
Protocols/API's that operate on this layer include: RPC, SQL, NETBIOS.
TransportTransport
This layer converts the data received from the upper layers into segments. The Transport layer is responsible for end-to-end (also called source-to-destination) delivery of entire messages. Provides end-to-end connectivity, it allows data to be transferred reliably and sequencing to guarantee that it will be delivered in the same order that it was sent. Provides services such as error checking and flow control (software).
Protocols that operate on this layer: TCP, UDP, NETBEUI.
Transport Transport Cont…Cont…
These protocols are either connectionless or connection-oriented:
Connection-oriented means that a connection (a virtual link) must be established before data can be exchanged. This can guarantee that data will arrive, and in the same order it was sent. It guarantees delivery by sending acknowledgements back to the source when messages are received. TCP is an example of an connection-oriented transport protocol.
A common example of connection-oriented communication is a telephone call: you call, the 'destination' picks up the phone and acknowledges and you start talking (sending data). When a message or a piece of it doesn't arrive, you say: "What!?" and the sender will retransmit the data.
Connectionless is the opposite of connection-oriented; the sender does not establish a connection before it sends data, it just sends without guaranteeing delivery. UDP is an example of an connectionless transport protocol.
A common example of connectionless communication is a Radio City, News paper, Television
NetworkNetwork This layer converts the segments from the Transport layer into
packets and is responsible for path determination, routing, and the delivery of these individual packets across multiple networks without guaranteed delivery. The network layer treats these packets independently, without recognizing any relationship between those packets, it relies on upper layers for reliable delivery and sequencing and also this layer is responsible for logical addressing (also known as network addressing or Layer 3 addressing) for example IP addresses
Examples of protocols defined at this layer: IP, IPX, AppleTalk, ICMP, RIP, OSPF, BGP, IGRP, EIGRP
Devices that operate on this layer: Routers, Layer 3 Switches.
Data LinkData Link The Data Links provides transparent network services to the
Network layer so the Network layer can be ignorant about the physical network topology and provides access to the physical networking media. Responsible for reassembling bits taken of the wire by the Physical layer to frames, makes sure they are in the correct order and requests retransmission of frames in case an error occurs. Provides error checking by adding a CRC to the frame, and flow control.
Examples of devices that operate on this layer are switches, bridges
Data Link layer has two sub layers: the LLC and the MAC sub layer.
Data LinkData Link Cont…Cont…
LLC sublayer :
The Logical Link Control is the upper sublayer of the Data Link layer. LLC masks the underlying network technology by hiding their differences hence providing a single interface to the network layer. This layer is also responsible for frames sequencing and acknowledgements.
MAC sublayer :
The Media Access Control layer takes care of physical addressing and allows upper layers access to the physical media, handles frame addressing, error checking. This layer controls and communicates directly with the physical network media through the network interface card. It converts the frames into bits to pass them on to the Physical layer who puts them on the wire (and vice versa)
PhysicalPhysical This layer communicates directly with the physical media, it is
responsible for activating, maintaining and deactivating the physical link. It handles a raw bits stream and places it on the wire to be picked up by the Physical layer at the receiving node. It defines electrical and optical signaling, voltage levels, data transmission rates and distances as well as mechanical specifications such as cable lengths and connectors, the amount of pins and their function.
Devices that operate on this layer: HUB, repeaters and WAN interfaces such as RS-232,, BRI, V.24, V.35, X.25 and Frame Relay.
SummarySummaryWhat basically happens when data passes from Host A to Host B:
1. Application, Presentation and Session layer take user input and converts it into data,
2. Transport layer adds a segment header converting the data into segments,
3. Network layer adds a network header and converts the segments into packets ,
4. Data Link layer adds a frame header converting the packets into frames,
5. MAC sub layer converts the frames into a bits which the Physical layer can put on the wire.
The steps are known as the 5 steps of data encapsulation. When the bits stream
arrives at the destination, the Physical layer takes it of the wire and converts it
into frames, each layer will remove their corresponding header while the data
flows up the OSI model until it is converted back to data and presented to the
user, this is known as de-capsulation.
TCP/IP Protocol
Introduction to TCP/IP The TCP/IP Suite defines a set of rules to enable
computers to communicate over a network. TCP/IP provides end-to-end connectivity specifying how data should be formatted, addressed, shipped, routed and delivered to the right destination .
Application Layer Handles high-level protocols, issues of
representation, encoding, and dialog control.
Transport LayerFive basic services:• Segmenting upper-layer application data• Establishing end-to-end operations• Sending segments from one end host to another end
host• Ensuring data reliability• Providing flow control
Internet LayerBest path determination and packet switching
IP as a Routed Protocol
IP is a connectionless, unreliable, best-effort delivery protocol.
As information flows down the layers of the OSI model; the data is processed at each layer.
IP accepts whatever data is passed down to it from the upper layers.
Packet Propagation and Switching Within a Router
Network Access Layer The network access layer is concerned with all of the issues that an
IP packet requires to actually make a physical link to the network media. It includes the LAN and WAN technology details, and all the details contained in the OSI physical and data link layers.
Types of cables
Coaxial Cable:• widely used for radio frequency applications• not susceptible to the effects of
– RFI– EMI
• Ethernet originally used coaxial cables• longer distances & higher transmission rates
– 10base2 - 200m (185m), 10 Mbps– 10base5 - 500m, 10 Mbps
• Ethernet/802.3 coax - 50, ARCNET coax 93
Types of cables cont…
Coaxial – cont…• Advantages:
– higher speeds than UTP– supports broad band (multi channel) LANs
• Disadvantages:
– easily damaged– difficult to work with– expensive than UTP– for different LANs specific coax types needed
Types of cables cont…
Twisted Pair• The type depends on:
– no. of pairs– no. of twists per unit length– gauge of the wire– type of insulation
• Shielded Twisted Pair (STP):– expensive– higher data rate– easy to work with
Unshielded Twisted Pair (UTP)
• Grouped into categories based on quality
• Generally used in LAN
• Cat 5 cable• RJ45
connector
Types of cables cont…
• Un-shielded Twisted Pair (UTP):– low cost– lower data rate– limited length– easy installation– flexible configuration (when star wired)– supports many LANs and voice communication in the
same cable type– easy fault isolation
Unshielded Twisted Pair (UTP)
• Adv– Does not require grounding like STP, easier to add
connectors– Thinner, more flexible to install– Same data speeds as other copper media
• Disadv– More susceptible to electrical noise and interference– Shorter cabling distance (100m when used for
Ethernet LANs)
Types of cables cont…
• UTP Categories:– category 3
• Up to 16 Mbps
• used for 10baseT Ethernet & 4 Mbps Token Ring
– category 4• Up to 20 Mbps
• used for 16 Mbps Token Ring
– category 5• Up to 100 Mbps
• 100baseT Ethernet
Fiber Optic Cable
Fiber Optic Cable
• Thin wire (usually very pure glass or plastic) surrounded by a reflective cladding that is used to transmit optical signals (light)
• Copper wire cables transmit signals electrically, whereas fiber-optic cables transmit signals by means of light
• More expensive than copper wires, more skill to install
Fiber Optic Cable
• Not susceptible to lightning, electromagnetic interference (EMI), or radio frequency interference (RFI), and does not generate EMI or RFI
• Much greater bandwidth• Greater transmission distances• Excellent signal quality
Fiber Optic Cable
• More secure (difficult to tap)
• Thin, requires little space in a conduit
• Lightweight, easy to install
• Better resistance to environment factors, e.g. water
• Generally used to link LANs, WANs, or as backbone of large networks
Types of cables cont…
• Fibre Optics• Advantages:
– no susceptibility to electrical & magnetic interference– allows electrical isolation between LAN segments– difficult to tap– very high data rates– longer cabling distances
• Disadvantages:– expensive– difficult to install– easy to damage
Types of cables cont…
Fibre Optics cont..• backbone cables typically contain 12 or 24 fibres
– multi-mode and single mode types– diameters:
• Multimode– 62.5 m or 50 m core, 125 m cladding (human hair – 100 m)
• single mode– 8 – 10 m core, 125 m cladding
– multi mode:• signal jitter at far end can occur• easy coupling of the light source to the cable
Types of cables cont…
• bandwidth:• expressed as MHz-km
– e.g.: 200 MHz-km 200 MHz, 1 km, or 100 MHz, 2 km
• connectors:• ST (straight tip) – for 10 BASE FL• SC (subscriber connector) – for 100 BASE FX and
1000 BASE FX• MT-RJ – for 1000 BASE FX – more compact
Cable splicing and fibre termination should be done by specialized people – requires skilled personnel and proper equipment
Fiber Optic Cable
• Fiber Optics Types:– Multi-mode cable
• Less expensive• Less expensive LED transmitters are used• Larger core, multiple angles of entry
– Single-mode cable• More expensive• More expensive laser transmitters are used• Significant longer cabling distances• Skinny core, only one angle of entry
Fiber Optic Cable
Types of cables cont…
Other LAN Media• Infrared
• modulated infrared signals passed through open space
• laser beam• modulated laser beams passed through open space
• Microwave• high frequency radio waves passed by line of sight
transceivers
• Radio• earlier low speeds (9.6 - 230 kbps) - now 2-10 Mbps• used for mobile LAN stations when cabling is not possible
Cabling Topologies
• Linear topology– uses terminators
• Star topology– uses a hub (concentrator or Multi-station
Access Unit (MAU))• star wired bus
– signals passed to all stations as in a bus
• star wired ring– signals passed from one station to the other by the hub
Connectors
• UTP:• RJ-11 (6 pins)• RJ-45 (8 pins)
– pin-outs will differ according to LAN type
• Thin Coaxial(10base2):• BNC (BayoNet Connector)• Terminator 50
• Thick Ethernet (10base5)• Transceiver• Attachment Unit Interface(AUI) < 50
Interfaces
• AUI – Attachment Unit InterfaceMedium independent attachment for 10 Mbps media systems
• MAU – Medium Attachment Unit• MDI – Medium Dependent Interface• MII – Medium Independent Interface• GMII – Gigabit Medium Independent Interface• TBI – Gigabit Ten-Bit Interface
To accommodate 8B/10B signal encoding in Gigabit Ethernet if 1000 BASE X is used
• GBIC – Gigabit Interface ConverterHot swappableMedia signaling components are contained
Interfaces cont…
Hub
DTE
10BASET internal transceiver (MAU)
MDI connector (RJ 45)
DTE
External transceiver (MAU)
AUI cable
Ethernet interface
AUI connector MII (15 pin)
DTE
40 pin MII connector for 100 BASE T
GBIC
2 SC connectors to fibre optic 20 pin connector to
Ethernet port
Cable Types• UTP – 10 BASE T
– Voice grade cabling– RJ-45 jack used– 100m maximum– 300mV signal squelch level (to eliminate cross talk signals)
• but after 100m, due to attenuation, data signals also will go below this
– 100 impedance (in some implementations 120 )0 high
-1 V DC offset
-2 V low
300 mV
300 mV
Cable Types cont…
• 100 BASE T– unshielded or shielded (for Token Ring)
twisted pair– 100m, 100, RJ-45 jack– 40 pin MII connector also may be used with
an external transceiver (not commonly used)– data is scrambled to eliminate electro-
magnetic effects
Cable Types cont…
• 100 BASE FX– 40 pin MII may be used– if transceiver is built-in, fibre optic can be directly
connected– Non-Return-to-Zero, Invert-on-Ones (NRZI) encoding
is used– Peek optical transmission power is 200-400 W for
62.5/125 m fibre– No data scrambling needed– Two strands of multi-mode fibre optics are used for Tx
and Rx
Cable Types cont…
• 1000 BASE T– Gigabit Ethernet twisted pair – defined by 802.3ab– UTP all 4 pairs are used – requires CAT-5 or higher quality cables
• All patch panels also should be of high quality
– Each pair has Tx and Rx wires (total of four Tx and four Rx wires in a cable)• hence total of 8bit at a time• 125 Mbaud achieves 1000 Mbps
– A combination of signaling and encoding is used to achieve the speed– No external transceivers or MIIs available – requires a built in transceiver– Digital Signal Processing (DSP) is used to handle cross talk
• echo cancellation• near end cross talk (NEXT) cancellation• far end cross talk (FEXT) cancellation• signal equalization for distortion compensation
– Auto negotiation possible (10/100/1000 Mbps) if the interface supports that
Cable Types cont…
• 1000 BASE X– Gigabit Ethernet for fibre optic– SX – Short Wave Length
• Most widely used• Less expensive• Short distance• Inside buildings
– LX – Long Wave Length• 500 m• long haul version – 10 km• extended reach version – 70-100 km
– CX – Short Copper Jumper• 25 m maximum• used for linking equipment in computer rooms, racks etc.
Structured Cabling– TIA
• Telecommunications Industry Association
– EIA• Electronics Industries Association
– TIA/EIA 568 A• Commercial Building Telecommunications Cabling Standard
– Aim• To provide a generic vendor independent cabling system to
support both voice and data
– Similar international standard• ISO/IEC 11801:1995
• Generic cabling for customer premises
• (IEC: International Electrotechnical Commission)
What TIA/EIA 568 A specifies
– horizontal cables– backbone cables– interconnection equipment– telecommunication closets (place where hubs,
switches, connectors, etc. are placed)– equipment rooms– cable pathways– uniform administration schemes– grounding practices
Elements of Structured Cabling
Building Entrance Facilities – Cables– surge protection equipment– connecting hardware for linking the cables
inside the building
Elements of Structured Cabling cont…
Equipment Rooms– More complex equipment– Major cable terminations– Grounding equipment
Elements of Structured Cabling cont…
Building Backbone Cabling– Using star topology– Provides connections between
• Telecommunication closets• Equipment rooms• Entrance facilities
Elements of Structured Cabling cont…
Telecommunications Closets– Also called wiring closets– Provides a location for the termination of the
horizontal cabling on a given floor of a building– Mechanical cable terminations and cross connects for
the horizontal and backbone cabling system– Interconnection equipment (Ethernet hubs and
switches etc.)
Elements of Structured Cabling cont…
Horizontal Cabling– Extends from the telecommunications closets
to the communications outlets located in the work area
– Work area outlets and patch panels (used for cable termination) are also included
– Patch cables
Elements of Structured Cabling cont…
Work Area– An office space– Computers and other equipment are located– Telephones and other devices connecting to
the communications outlet on the wall
Structured Cabling Topology
Structured cabling described in TIA/EIA 568 is based on star topology
• Within a building no more than two levels of hierarchy– i.e. the cable should not go through more than one
“Intermediate Cross Connect” (IC) device between the “Main Cross Connect” (MC) and “Horizontal Cross Connect” (HC)
Some Terms
• ER – Equipment Room• HC – Horizontal Cross Connect – located in a
wiring closet. Should be less than 90 m (patch panel cables should be less than 6m)
• IC – Intermediate Cross Connect• MC – Main Cross Connect – terminated in an
equipment room• TC – Telecommunications Closet• WA – Work Area
Advantages of Structured Cabling
• Central wiring hubs make it easy to manage moving, adding, changing, etc.
• Central cabling points provide faster trouble shooting
• Independent point to point links prevent cable problems – does not affect other links
• Easier migration to newer technologies – no or less re-cabling required if hubs, switches, routers etc. upgraded in most cases
• Physical security for central equipment room
Cables used for EIA/TIA 568
• Category 5 – 100 UTP– Up to 100 MHz
• Category 5e (Enhanced category 5)– With enhanced testing– For gigabit Ethernet
• Fibre optic
LAN UTP Cabling Standards
Category
Purpose Comments
1 Telephones Not suitable for data
2 Token Ring Supports 4Mbps Token Ring
3 Telephones and 10BASE-T
4 Token Ring Supports 16Mbps Token Ring
5 Ethernet 10BASE-T and 100BASE-T
5e Ethernet Supports Gigabit Ethernet
6 Ehernet Officially supports 1Gbps, working for 10Gbps support
Ethernet LAN Media and Connectors
Ethernet Types Media Max Segment Length
Connector
10BASE2 50-ohm coax(Thinnet)
185m BNC
10BASE5 50-ohm coax
(Thicknet)
500m Attachment unit interface (AUI)
10BASE-T Cat 3,4,5 UTP
100m RJ45
100BASE-TX Cat 5 UTP 100m RJ45
100BASE-FX 62.5/125 micron multimode fiber
400m Duplex media interface connector (MIC), ST, or SC
1000BASE-T Cat 5 UTP 100m RJ45
UTP Cable Pinouts
• Key concepts– Ethernet devices (at 10 and 100Mbps Ethenet) use
one pair of wires to transmit data– Ethernet devices (at 10 and 100Mbps Ethenet) use
another pair of wires to receive data– Two pairs of wires are required
• Types– Straight-Through Cable– Crossover Cable– Console Connection and Rollover Cable
Straight-Through Cable
• To connect an end-user device and a LAN hub or switch
• PC’s NIC uses– Pin 1, 2 to transmit– Pin 3, 6 to receive
• LAN hubs, switches (the other end)– Pin 3, 6 to transmit– Pin 1, 2 to receive
Straight-Through Cable• TIA/EIA-T568-B or A on BOTH ends of the cable
TIA/EIA 568-A
Crossover Cable
• To connect two devices that both want to send on the same pins (two devices of similar ‘type’, e.g. two PCs)
• BOTH sides use– Pin 1, 2 to transmit– Pin 3, 6 to receive
Crossover Cable• One side is T568-A and T568-B one the other (10BaseT,
100BaseT)• Special arrangement for 1000BaseT
How to create Console cable
• Preparation We should prepare the following two, as well as a Cisco and a
console-terminal.
RJ45-DSub9Pin Cable Changer (In=RJ45 Female, Out=DSub9Pin Female)
• How to connect them
D Sub9 Pin Female
123456789
12345678
RJ 45 Female
How to choose?
• Two groups of devices– PC, router, server, AP (use pins 1 and 2 to transmit)– Switch, hub, bridge, repeater (use pins 3 and 6 to transmit)
• When connecting two devices that are similar in regard to which pins they use to transmit, use a crossover cable– e.g. Switch to Switch, Switch to Hub, Hub to Hub, Router
to Router, PC to PC, Router to PC• When connecting two devices that differ in regard to
which pins they use to transmit, use a straight-through cable– e.g Switch to Router, Switch to PC, Hub to PC
Network Topologies
• The physical or logical arrangement of computers of computers, transmission media, and other components
• Types of network topologies– Bus topology– Ring topology– Star topology– Hybrid topology
Bus Topology
• All nodes are connected in sequence on a single cable
• Used most often on peer-to-peer networks
• Networked computers communicate with each other
• One computer transmits data at a time– Access methods avoid data
collisions– Data is transmitted in
“packets”
Ring Topology
• Nodes are laid out in a ring
• Token (data packet) flows in one direction from device to device
Star Topology
• Nodes connect to a central communications device (switch)
• A node sends a signal to the switch, which retransmits it to the other nodes
• A node accepts only signal addressed to it
LAN Equipment
• Repeaters/Hubs:– At Physical layer– Ethernet can be extended using repeaters– 10baseT concentrator is a multi port repeater– amplifies the signal and increase the overall distance –
restores the amplitude of the signal– restores signal symmetry– re-timing can be done– can be used for dissimilar media– 7 hops maximum– different LANs cannot be converted – no protocol conversion
LAN Equipment cont…
• Bridges/Switches:– Operates at Data-link layer or MAC layer– Multiple LANs can be connected– Can connect similar LANs with dissimilar media– Can link LANs of different speeds– Passes Packets to the other segment only if
addressed to a node in that segment– Builds an address data base dynamically (a table with port –
address combinations) and use this to filter traffic– Hence collision domains are extended only if required
– Management software could be used to manage the switches
LAN Equipment cont…
• Routers:– At Network layer– Can connect dissimilar LANs on the same protocol– Some routers have support for may protocols and
protocol conversion– Can build large complex networks with complex traffic
routing– Limits the flow of broadcasts– Load sharing and balancing can be done– Complex features as Network Address Translation
(NAT), authentication, firewalling, etc. possible
Classifications of Networks• Local area network (LAN):
– Nodes are within a small geographic region:• Homes• Schools• Small businesses
• Wide area network (WAN):– LANs connected over long distances:
• Computers linked over large geographic locations (few miles to thousands of miles
• Use telecommunications lines
• Metropolitan area network (MAN)– Metropolitan area network– Computers linked together within a city or county
• Personal area network (PAN)– Wireless devices connected in close proximity to each other
• Intranet– Private corporate network, not accessible to non-employees– Protected by a firewall
Introduction to WAN
• Connect devices separated by wide geographical areas
• Use services or RBOCs (Regional Bell Operation Co.), Sprint,MCI, etc.
• Uses various types of serial connections
• Companies use a WAN to connect sites so that information can be exchanged between distant offices.
WAN devices• routers – provides WAN interface ports
• switches - provide connectivity for voice, data, and video communication
• modems - interface voice-grade services – CSU/DSUs that interface T1/E1 services– TA/NT1s (ISDN modem) that interface ISDN services
• communication servers – dial-in and dial-out user communication– manages the dial-up– log-on authentication
Routers in a WAN• Computers have four basic components:
– CPU
– Memory
– Interfaces
– Bus
• A router also has these components;
therefore it can be referred to as a computer• Routers need the Internetworking Operating
Software (IOS) to run configuration files just like a computer needs an OS to run software applications
Router components
RAM• RAM, or dynamic RAM (DRAM) is usually
logically divided into main processor memory and shared input/output (I/O) memory– Stores routing tables – Holds ARP cache – Holds fast-switching cache – Performs packet buffering (shared I/O memory)– Maintains packet-hold queues – Provides temporary memory for the configuration file
of the router while the router is powered on – Loses content when router is powered down – Can be upgraded by adding Dual In-Line Memory
Modules (DIMMs)
NVRAM and Flash• NVRAM
– Store backup/startup config file– Retains contents when powered down or restarted.
• Flash– Erasable programmable ROM (EPROM)– Upgraded with Single In-Line Memory Modules
(SIMMs) or Flash Cards (PCMCIA) without removing chips on board
– Multiple versions of IOS can be stored in the flash– Contents remain when powered down – In most routers the IOS is transferred to RAM during
the boot process. In others the IOS may be run directly from flash
ROM and Interfaces
• ROM– Maintains instructions for POST– Stores bootstrap program and basic IOS.– Software upgrades in ROM require replacing chips on
the CPU– Stores a scaled down version of the IOS
• Interfaces – Network connections through which packets enter
and exit– Located on motherboard or on a separate module
Bus
• Buses – Most routers contain a system bus and a CPU bus. – The system bus transfers packets between
the CPU and interfaces. – The CPU bus transfers instructions and data
between the CPU and specified memory addresses
Segmentation with Routers
• Can be used to segments LANs, but generally used as a WAN device
• Routers have both LAN and WAN interfaces• Routers are the backbone devices of large
intranets and of the Internet • A correctly configured internetwork
provides: – Consistent end-to-end addressing – Addresses that represent network topologies – Best path selection – Dynamic or static routing – Switching
Router role in a WAN
• WANs operate at the Physical and Data Link layers
• The standards and protocols used in WANs at Layer 1 and 2 are different from those used in LANs at the same layers
• Data link layer protocols describe how frames are carried between systems on a single data link
• Physical layer describes the interface between the DTE and the DCE
WAN Layer 1 and 2 Protocols
HDLC, PPP, Frame Relay, SDLC, SLIP, X.25, ATM, LAPB, LAPD, LAPF
EIA/TIA-232, EIA/TIA-449, V.24, V.35, X.21, G.703, EIA-530, ISDN, T1, T3, E1, E3, xDSL, SONET (OC-3, OC-12, OC-48, OC-192)
Lab Setup• Unlike the lab setup, the serial cables in the
real world are not connected back to back• In the lab, devices that make up the WAN
cloud are simulated by the connection between the back-to-back DTE-DCE cables.
Ports• 3 types of interfaces
– LAN-• Ethernet,Token Ring or FDDI
– WAN-• Serial, ISDN, and integrated Channel Service Unit
(CSU)
– Management-• Console and Aux port
• EIA-232 asynchronous serial ports connects to the computers COM port
• Computers must use a terminal emulation program that provides a text-based session with the router
• DB9-RJ45 connector and a rollover cable
• not designed as networking ports
Management port connections
•Recommended for initial configuration •Displays router startup, debugging, and error messages by default •Used for password recovery procedures
Connecting Console Interfaces
1. Configure terminal emulation software on the PC for: – The appropriate com port – 9600 baud – 8 data bits – No parity – 1 stop bit – No flow control
2. Connect the RJ-45 connector of the rollover cable to the router console port.
3. Connect the other end of the rollover cable to the RJ-45 to DB-9 adapter.
4. Attach the female DB-9 adapter to a PC
Connecting LAN interfaces
• A router is a host that communicates with the LAN via a hub or a switch using a straight through cable
• The router is connected to the LAN using an Ethernet or Fast Ethernet interface
• A 10/100BaseTX router interface requires UTP, Cat 5 or better cable
Connecting WAN interfaces
• The customer premises equipment (CPE) is often a router and is the data terminal equipment (DTE)
• The DTE is connected to the service provider using a data circuit-terminating equipment (DCE) device, commonly a modem or channel service unit/data service unit (CSU/DSU).
• The DCE is used to convert the data from the DTE into a form acceptable to the WAN service provider.
Connecting WAN interfaces
IP Addressing
IPv4 Addressing Overview
Internet address’s architecture Classes of IP addresses Subnet mask
IP Address
An IP address is a 32-bit sequence of 1s and 0s.To make the IP address easier to use, the address is usually
written as four decimal numbers separated by periods. This way of writing the address is called the dotted decimal
format.
IP Address
Every IP address has two parts: NetworkHost
The Class D address class was created to enable multicasting.
IETF reserves Class E addresses for its own research.
Address Classes(32 Bit Address 232 = 4.2 billion possible addresses)
• There are 5 different address classes.
• Only 3 are in commercial use at this time.
• You can determine the class of the address by looking at the first 4 bits of the IP address:
– Class A begin with 0xxx, or 1 to 126 decimal– Class B begin with 10xx, or 128 to 191 decimal– Class C begin with 110x, or 192 to 223 decimal– Class D begin with 1110, or 224 to 239 decimal– Class E begin with 1111, or 240 to 254 decimal
IP Address
Reserved IP AddressesCertain host addresses
are reserved and cannot be assigned to devices on a network.
An IP address that has binary 0s in all host bit positions is reserved for the network address.
An IP address that has binary 1s in all host bit positions is reserved for the broadcast address.
IP Private AddressesNo two machines that connect to a public
network can have the same IP address because public IP addresses are global and standardized
Private IP addresses are a solution to the problem of the exhaustion of public IP addresses. Addresses that fall within these ranges are not routed on the Internet backbone:• Connecting a network using private addresses to the Internet requires the usage of NAT
Subnet Mask Address
A subnet mask allows you to identify which part of an IP address is reserved for the network, and which part is available for host are.
In summary, knowing the subnet mask can allow you to easily calculate whether IP addresses are on the same subnet, or not using bitwise AND gate (A Boolean operator that returns a value of TRUE if both its operands are TRUE, and FALSE otherwise)
.
Default Subnet Masks
Class A - 255.0.0.011111111.00000000.00000000.00000000
Class B - 255.255.0.011111111.11111111.00000000.00000000
Class C - 255.255.255.011111111.11111111.11111111.00000000
Establishing the Subnet Mask Address
To determine the number of bits to be used, the network designer needs to calculate how many hosts the largest subnetwork requires and the number of subnetworks needed.
Subnetting
• Subnetting an IP network can be done for various reasons including:
– Organization– Use of different physical media– Preservation of address space– Security– Control network traffic
Subnetting
• Subnetting is a way of taking an existing class license and breaking it down to create more Network Addresses.
• This will always reduce the number of host addresses for a given network.
• Subnetting makes more efficient use of the address or addresses assigned to you.
How Does Subnetting Work?
• Additional bits can be added (changed from 0 to 1) to the subnet mask to further subnet, or breakdown, a network.
• When the logical AND is done by the computer, the result will give it a new Network (or Subnet) Address.
• Remember, an address of all “0”s or all “1”s cannot be used in the last octet (or host portion). All “0”s signify the Network Address and all “1”s signify the broadcast address
Network Security
• Authentication– User ID and password used to access the network
• Access privileges– Enable access to certain network systems
• Physical protection measures– Restrict physical access to sensitive network
equipment– Magnetic card readers– Biometric access devices
• Firewalls– Prevent access to the network by unauthorized users– Composed of software and/or hardware– Screen and validate data packets– Bastion host/proxy server
Network Firewall Layout
Computer Threats
• Cyber-crimes are criminal acts conducted through the use of computers by Cyber-criminals.
• Cyber criminals are individuals who use computers, networks, and the Internet to perpetrate crime.
• The existence of cyber crime means that computer users must take precautions to protect themselves
Hackers • Anyone who unlawfully accesses a computer system• Types of hackers:
– White-hat, hackers who break into systems just for the challenge of it
– Black-hat, hackers who use their knowledge to destroy information or for illegal gain
– Script kiddies use tools created by skilled hackers
What Hackers Do
• Steal information from computers:– Credit card numbers– Bank account numbers
• Internet packet sniffing• Commit identity theft
Denial of Service Attacks
• Backdoor programs – Trojan horse, allow hackers to take almost complete
control of your computer without your knowledge– Zombies
• Denial of service attacks (DoS)
How Hackers Gain Access
• Direct access:– Hacking software
• Indirect access:– Internet connection– Logical ports
Computer Safeguards Firewalls
• Software programs or hardware designed to close logical ports to invaders– A firewall is built into Windows XP– More robust firewalls are available from other
vendors.– Firewalls are critical if you
have an always-on broadband connection.
Computer Threat - Viruses
• A program that attaches itself to another program and spreads itself to other computers
• Viruses are hidden within the code of a host program
• Replicate themselves:– Slow down networks
• Secondary objectives:– Annoying messages– Delete files on the hard drive– Change computer settings
How Does a Computer Catch a Virus
• Viruses copy themselves • Infect a file on your computer• Viruses spread by sharing disks• E-mail attachments are the most likely source of a virus
Types of Viruses
• Boot-sector viruses:– Replicate themselves in the boot sector of the hard drive
• Logic bombs:– Activate when certain conditions are met
• Time bombs:– are viruses that are triggered by the passage of time or
on a certain date.
• Worms:– Travel between systems through networks
Types of Viruses
• Script viruses:– Hidden on Web pages– Mini programs
• Macro viruses:– Attached to documents– Series of commands
• Trojan horses:– Backdoor programs– Control remote computers
Virus Classifications
• Polymorphic viruses:– Periodically rewrite themselves to avoid
detection
• Multipartite viruses:– Infect multiple file types
• Stealth viruses:– Erase their code from the hard drive and
reside in the active memory
Antivirus Software
• Programs designed to detect viruses:– Scan files looking for virus signatures (unique code)– Provides options for deleting or fixing infected files
• Detect known viruses• Antivirus programs need to be updated frequently
Lease Line Looping System
NIC JaipurDDF,Jaipur
NTR, Jaipur
District NICMODEM
NTR, DistrictExchangeMODEM
District NICRouter
BSNLExchange
District NICSwitch
FIBER COPPERFIBER
V 35 Blue Cable
COPPER
Video Conferencing
VC Over IP Network
Distance < 100mSwitch Switch
IP Address: 172.16.1.2/16Gateway: 172.16.1.1
IP Address: 172.16.2.2/16Gateway: 172.16.1.1
NIC VC over Lease Line Network
NIC – (District Centres) Kota, Bikaner, etc.
MCU
NIC, Delhi
NIC Jaipur
Switch
Users
NIC , Jaipur
NIC-District Router Router
Lease LineLease Line
Lease Line
ISDN BRI Line
Switch
NTU/V.35NTU/V.35
E1/G.703 E1/G.703
NT1
NT1
ISDN PRI Line
BSNL Network
ISDN VC Network
Jaipur
ISDNNetwrok
ISDN BRI Line
NT1 NT1
ISDN BRI Line
ISDN BRI Line
NT1
Jodhpur
Kota
Features Phone
Features Phone
Troubleshooting of VC
PING
VC Set Top Box IP
VC Gateway
NICNET Gateway Status of Switch/ Router/ MODEM BSNL NICNET iNOC
Troubleshooting of VC
Cables
Audio Video Cable (Color Coding)
LAN Cable
UTP Cable (Rx & Tx Pair)
Straight & Cross Cable
ISDN Cable (Rx & Tx Pair) MIC
Troubleshooting of VC
POWER Supply
220 VC
N. E. L.
N-E Voltage: 2 Volt Voltage of ISDN line will be 96 Volt DC. Voltage of PSTN line will be 48 Volt DC.
Troubleshooting of VC
• ISDN problems.Check the power of NT box, voltage of ISDN line it will be 96 Volt DC. If both are ok then contact to BSNL.
• In case of Audio problems, check the volume level in TV as well as VC system and Mic.
• In case of Video problems, check the AV selection in the TV, ISDN line.
System Maintenance and Troubleshooting
Network Troubleshooting
Troubleshooting Windows Startup
Problems
Repairing Internet Explorer 6
Troubleshooting MS Outlook
Network Troubleshooting
We will learn how to troubleshoot basic network related problems
UN IT
ONE
Troubleshooting Windows Networks
Determine the TCP/IP Settings: In XP, open the Network
Connections folder, right click the LAN connection, and click
Status | Support | Details.
Troubleshooting Windows Networks
Description of TCP/IP Settings:
Here are the TCP/IP settings that are used in network
troubleshooting:
IP Address:
Unique address assigned to a network adapter. A computer with multiple network adapters has an IP address for each one, and each one must be in a different subnet.
Subnet Mask:
Used in conjunction with the IP address to determine which subnet an adapter belongs to. At the simplest level, communication is only possible between two network adapters when they’re in the same subnet.
Troubleshooting Windows Networks
Default Gateway:
IP address of a computer or router, on one of this computer’s local area networks, that knows how to communicate with subnets not present on this computer. For an Internet connection, the default gateway is a router belonging to your Internet service provider, and all access to sites on the Internet goes through it. For an ICS client, the default gateway is the ICS host. If you use a hardware router, it serves as the default gateway.
DHCP Server:
If an adapter is configured to obtain an IP address automatically, this is the address of the server that provides it. It could be your ISP, an ICS host, or a hardware router.
DNS Servers – IP address of one or more Domain Name Server computers. DNS servers translate Internet names (like 3i-infotech.com) to their IP addresses (like 63.146.109.227).
Pinging:
Troubleshooting Windows NetworksTroubleshooting Windows Networks
Troubleshooting Windows Networks
The ping command is the basic tool for testing TCP/IP connectivity. It sends a special packet (called ICMP Echo) to a particular IP address and looks for a reply. If everything is working right, the reply comes back. If not, the ping times out in a few seconds. By default, the ping command repeats the process four times. Here’s an example of an ICS client computer pinging a Windows XP Home Edition ICS host, using the host’s IP address and its computer name.
Troubleshooting Windows Networks
When ping fails, you’ll see one of these error messages:
Request timed out :
The IP address is valid, but there’s no reply from it. If the IP
address is on a local area network, the most likely cause is a
firewall program blocking the ping.
Unknown host <name> or Ping request could not find host <name>:
The computer name doesn’t exist on the local area network. Make
sure that NetBIOS over TCP/IP is enabled.
Destination host unreachable:
The IP address isn’t on a local area network, and the default
gateway can’t access it. Either there’s no default gateway, its
address is wrong, or it isn’t functioning.
Troubleshooting Windows Networks
Command Target What Ping Failure Indicates
ping 127.0.0.1 Loopback address
Corrupted TCP/IP installation
ping localhost Loopback name Corrupted TCP/IP installation
ping 192.168.1.101
This computer’s IP address
Corrupted TCP/IP installation
ping winxp This computer’s name
Corrupted TCP/IP installation
ping 192.168.1.123
Another computer’s IP address
Bad hardware or NIC driver
Series of ping commands to use in finding where a problem occurs on a local area network
Troubleshooting Windows NetworksCommand Target What Ping
Failure Indicates
ping w.x.y.z Default Gateway
Default Gateway down
ping w.x.y.z DNS Server DNS Server down
ping w.x.y.z Web site IP address
Internet service provider or web site down
ping www.something.com
Web site name
DNS Server down or web site down
Network troubleshooting methodology
OSI model
The basis of each of troubleshooting approaches is the
Seven-Layer OSI Reference Model:
Layer 1: Physical
Layer 2: Data Link
Layer 3: Network
Layer 4: Transport
Layer 5: Session
Layer 6: Presentation
Layer 7: Application
Network troubleshooting methodologyBottom-up Approach:
The bottom-up approach as the name implies, start at the
bottom—Layer 1, the physical layer—and work your way up to
the top layer (application). The physical layer includes the network
cable and the network interface card. So if you encounter a
broken or disconnected network cable, there's probably no need
to do anymore troubleshooting. You must resolve any physical
layer problems before moving on. After fixing the problem, check
to see if the trouble still exists. If so, move on to troubleshooting
the data link layer
Network troubleshooting methodology
Top-down
Once again, the name of this methodology implies the approach.
With the top-down method, start at the top of the OSI model (i.e.,
the application layer) and work your way down to the bottom
layer (i.e., physical).
Divide and conquer
This approach involves a little more intuition. With the divide and
conquer method, start at whichever layer you best feel is the root
cause of the problem. From there, you can go either up or down
through the layers.
Network troubleshooting methodologyChoosing an approach
Which approach you decide to use may depend on where you
believe the problem lies. For example, if a user is unable to
browse the Web and you think most users have a lot of problems
with spyware and Internet Explorer settings, then you may want to
start with the top-down approach. On the other hand, if the user
mentions that he or she just connected a laptop to the network and
can't browse the Web, you might want to use the bottom-up
method since there's a good chance the user has a disconnected
cable or similar problem.
Troubleshooting Startup Problems
We will learn how to resolve common startup problems associated with booting Windows XP and Windows Server 2003 systems.
Troubleshooting Startup Problems
Windows may fail to start for a variety of reasons, and generally
speaking in order of decreasing likelihood here they are:
Hardware failure Bad driver Corrupt file or volume System misconfiguration Virus infection
Troubleshooting Startup Problems
Common error Messages & Probable Causes:
Symptom Probable Cause
"Invalid Partition Table"
"Missing Operating System"
Master boot record is corrupt due to hard disk errors or virus infection
“NTLDR is missing"
"A disk read error occurred"
System hangs after BIOS POST finishes
Boot sector is corrupt due to hard disk errors or virus infection
“Windows could not start because of a computer”
“disk hardware configuration problem"
"Could not read from selected boot disk"
"Check boot path and disk hardware “
Boot.ini file is corrupt, missing, or needs updating
"Windows could not start because the following file is missing or corrupt”
Boot volume is corrupt or the referenced system file is missing.
Troubleshooting Startup Problems
In addition to these error messages, a variety of other startup
problems can occur including:
Blue screens:
These are typically caused by hardware failure or driver problems
but can also be due to virus infection.
Hung system:
These are typically caused by buggy drivers or by registry
corruption but can also be due to virus infection.
Dialog box saying "One or more services failed to start”:
This is typically caused by misconfiguration or registry corruption
but can also be caused by application incompatibility of some
form.
Troubleshooting Startup Problems
How to resolve startup problems:
Last known good Configuration Option:
Restores the HKLM\System\CurrentControlSet portion of the
registry its version during the last successful logon to the system.
Safe mode: Starts Windows with a minimal set of drivers and
creates a record of which drivers load in %windir%\Ntbtlog.txt.
System Restore: Windows XP only feature to restore system to
previously saved configuration.
Recovery Console: Boots to a command line that allows you to
run various commands.
Troubleshooting Startup ProblemsHow to resolve startup problems:
Automated System Recovery (ASR):
Restores the boot volume from backup.
Repair:
Run Windows Setup from your product CD and select the option to
try and repair your installation
Troubleshooting Startup Problems
Problem Resolution Table:
Problem/Symptom Tool's) to Use
Corrupt master boot record
Corrupt boot sector
Recovery Console (fixmbr)
Corrupt or missing boot.ini Recovery Console (bootcfg /rebuild)
Corrupt system file Recovery Console (chkdsk)Restore from ASR backupPerform a Repair install
Corrupt registry Recovery Console (chkdsk)System Restore (XP only)Restore system state from backupPerform a Repair install
Troubleshooting Startup Problems
Problem Resolution Table:
Problem/Symptom Tool's) to Use
Blue screen Last known goodSystem Restore (XP only)Safe mode (roll back suspect driver using Device Manager)
Hung system Last known goodSystem Restore (XP only)Safe mode (roll back suspect driver using Device Manager)
"One or more services failed to start" Don't logon! Reboot and select last known good, log on, undo the last configuration steps you performed.Safe mode (undo last configuration steps you performed)
Repairing Internet Explorer 6
We will learn how to reinstall or to repair Internet Explorer 6 in Windows XP, We may have to do this if we have problems with Internet Explorer because of damaged files or missing registration information. In some cases, the steps to reinstall or to repair Internet Explorer 6 will also resolve problems in Microsoft Outlook Express
UN IT
THREE
Repairing Internet Explorer 6Methods to follow:
Method 1: Install Internet Explorer 7:
We may be able to resolve problems with Internet Explorer 6 if
we install Internet Explorer 7. Installing Internet Explorer 7
probably will not resolve problems with Outlook Express.
Method 2: Install Windows XP Service Pack 2:
If you do not want to install Internet Explorer 7, or for some reason
cannot do so, you may be able to resolve problems with Internet
Explorer 6 by installing Windows XP Service Pack 2. Additionally,
installing Windows XP Service Pack 2 may help resolve issues
with-Outlook-Express.
Repairing Internet Explorer 6Methods to follow:
Method 3: Repair Internet Explorer 6 by using the System File
Checker in Windows XP:
If you already have Windows XP Service Pack 2 installed, and you
do not want to install Internet Explorer 7, you may be able to
resolve problems with Internet Explorer 6 by running the System
File Checker.
To run the System File Checker, follow these steps:
1.Click Start, click Run type sfc /scannow, and then press ENTER
2.Follow the prompts throughout the System File Checker process.
3.Restart the computer when System File Checker process is complete
Repairing Internet Explorer 6Methods to follow:
Method 4: Reinstall Internet Explorer 6 by using the ie.inf file:
If you already have Windows XP Service Pack 2 installed, and you
do not want to install Internet Explorer 7, you may be able to
resolve problems with Internet Explorer 6 by using the ie.inf file to
reinstall Internet Explorer 6. To do this, follow these steps:
1.Click Start, click Run, type %systemroot%\inf, and then press Enter.
2.Find the Ie.inf file that is located in Windows\Inf folder.
3.Right-click the ie.inf file, and then click Install.
4.Restart the computer when the file copy process is complete.
Repairing Internet Explorer 6Method to follow if you have Internet Explorer 7:
If you have Internet Explorer 7, you can repair damaged files
or missing registration information in Internet Explorer 7. To
do this, follow these steps:
1.Start Internet Explorer 7.
2.On the Tools menu, click Internet Options.
3.On the Advanced tab, click Reset.
4.In the Rest Internet Explorer Settings dialog box,
click Reset to confirm.
Troubleshooting Ms Outlook Express
We will learn how to troubleshoot error messages when we send and receive e-mails.
We may receive an error message that is similar to one of the
following: “ No connection could be made because the target machine actively refused it”
“The server could not be found. (Account:account name, POPserver:'mail', Error
Number: 0x800ccc0d)”
“Task 'server name - Sending and Receiving' reported error (0x800ccc0f): 'The
connection to the server, was interrupted. If this problem continues, contact the
server administrator or Internet service provider (ISP)”
“Your server has unexpectedly terminated the connection. Possible causes of this include server problems, network problems, or a long period of inactivity.
Account. account name, Server: 'server name', Protocol: POP3, Server
Response: '+OK', Port: 110, Secure(SSL): No, Error Number: 0x800ccc0f”
“Task 'SMTP server name - Sending and Receiving' reported error (0x80042109):
'Outlook is unable to connect to your outgoing (SMTP) e-mail server. If you
continue to receive this message, contact the server administrator or Internet
service provider (ISP).”
Troubleshooting Ms Outlook Express
Troubleshooting Ms Outlook Express
You may also receive an error message that includes one or more of the following error codes:
*0x800ccc15
*0x80042108
*0x800ccc0e
*0x8004210b
*0x800ccc0b
*0x800ccc67
Troubleshooting Ms Outlook Express
CAUSES:
These error messages are frequently caused by one of the
following:
You are not connected to the Internet or a Network
Incorrect account settings
Your user profile in Outlook is damaged
An e-mail item on your POP3 server is damaged
Incorrect configuration of your AV software
Outlook Express has been removed from the computer or the installation is damaged
Incorrect configuration of personal firewall software
Troubleshooting Ms Outlook Express
Resolution:
The most common causes of these error messages are problems
with Internet connectivity and incorrectly configured account
settings in Outlook or Outlook Express.
Step 1: Verify that you are connected to the Internet.
Step 2: Verify your account settings
Troubleshooting Ms Outlook Express
Advanced Troubleshooting
Method 1: Start Outlook in safe mode
1.Click Start, and then click Run.
2.In the Open box, type outlook.exe /safe , and then click OK.
Starting Outlook in safe mode starts Outlook without extensions, the
preview pane, or toolbar customizations and could indicate a
damaged profile or conflicting third-party application or add-in.
Method 2: Create a new e-mail profile
We may be able to resolve these problems by creating a new e-
mail profile. For more information about how to create profiles in
Outlook,
Troubleshooting Ms Outlook Express
Advanced Troubleshooting
Method 3: Delete suspicious messages from your mailbox
If there is a damaged message in your mailbox, we can resolve
this by doing one of the following: Contact your ISP and ask them to delete any suspicious e-
mail. Delete any suspicious e-mail by accessing your mailbox by
using your ISP's Web-based e-mail program.
Method 4: Check your antivirus vendor's Web site for additional
suggestions
If your antivirus solution includes an e-mail scanning feature, you
May have to do additional configuration to use Outlook or Outlook
Express with the antivirus e-mail scanning feature.
Troubleshooting Ms Outlook Express
Advanced Troubleshooting
Method 5: Remove and then reinstall Outlook Express:
If Outlook Express has been removed from your computer or the
installation of Outlook Express is damaged, Outlook will not
function correctly and may generate one of the error messages
that are mentioned in the "Symptoms" section. To resolve this
problem, reinstall Outlook Express.
Method 6: Verify that all SMTP e-mail addresses in a distribution list
Are Valid:
If one SMTP address in a distribution list is corrupted or incorrectly
formed, error 0x8004210b can occur
Troubleshooting Ms Outlook Express
Advanced Troubleshooting
Method 5: Remove and then reinstall Outlook Express:
If Outlook Express has been removed from your computer or the
installation of Outlook Express is damaged, Outlook will not
function correctly and may generate one of the error messages
that are mentioned in the "Symptoms" section. To resolve this
problem, reinstall Outlook Express.
Method 6: Verify that all SMTP e-mail addresses in a distribution list
Are Valid:
If one SMTP address in a distribution list is corrupted or incorrectly
formed, error 0x8004210b can occur .
Method 7: Examine the configuration of your firewall software
THANK YOU
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