Networking Essentials those who wants to make career in Computer Networking

1. Networking
Essentials
Created by:
Vikas Gupta (CCNA),
Network Support Engineer,
Pune, India.

2. Network: Collection of inter-connected computer system.
Networking: Inter connection between the two or more computers are called the
networking. Using three types of networkare Intranet, Internet and Extranet (Eg. LAN, WAN
& MAN)
Bandwidth: Every line has an upper limit and a lower limit on the frequency of signals it
can carry. This limited range is called the bandwidth. Every line has a capacity of transmission
of data; the maximum amount of data that can be transferred in a single line is called
Bandwidth.
Collision Domain: Collision domain is an Ethernet term used to describe a network
collection of devices in which one particular device sends a packet on a network segment,
forcing every other device on that same segment to pay attention toit
Broadcast Domain: On a broadcast domain, a set of all devices on a network segment
hears all broadcasts sent on that segment
Interconnecting Devices
Bridges:
 Breakup the collision domain in LAN (Per port collision)
 Same as switch
 Bridges had only 2 to 4 port
Hub:
 Represent one collision domain and one broadcast domain
 It create congestion to Ethernet network
 Speed is divided with ports
 It is dumb to identify devices in a network
Switch:
 Provide more bandwidth to user
 Single broadcast domain
 By default switch break up the collision domain
 Each and every port in switch represent its own collision domain
 They uses the Hardware address (MAC address) to filter the network
Router:

3.  Router provide internetwork and provide communication to WAN
 It Break up broadcast domain & collision domain as well
 They don’t forward broadcast by default
 They filter the network based on logical address in Network Layer (IP address)
 Packet filtering (By using Access list)
 Packet Switching
 Path selection
TCP/IP Network Model
TCP/IP (Transmission Control Protocol / Internet Protocol):
 It is occasionally called as DoD Model (Department of Defense) due to foundational
influence of ARPANET in 1970’s
 TCP/IP come into existent before OSI model
 TCP/IP is based on protocol not a layer based model
 TCP/IP model is created on the basis of protocol
 TCP/IP provide connectionless service in Network layer
 Both connection oriented and connectionless in Transport Layer
Fig.: TCP/IP Model with Protocol in each layer
Application & Services

4. Telnet (Teletype Network):
 Telnet is chameleon (Changeable) of protocol
 It’s specialty is terminal emulation
 It allow a user on remote client machine called tenet client, to access the resources of
another machine (Telnet Server)
 This project is actually software image-a virtual terminal that can interact with chosen
remote host
 This terminal gives option to User to select the menu and application on server
 All data even login data is sent in clear text format, this can be a security risk
 For telnetting it necessary to have telnet is enable in both transmitting and receiving
party
FTP (File Transfer Protocol):
 It just not a protocol it’s a Program so that user can perform operation on transfer
 FTP allows access to both file and directory and operation to relocating in other place
 FTP work with Telnet to login into FTP server
 After login User subjected for authentication and probably User name and Password
enable by administrator
 FTP only access the file and folder it cannot executing the file
TFTP (Trivial File Transfer Protocol):
 TFTP having less feature than FTP it is stripped-down
 It is very easy to use and fast too
 Can Use only for send and receive
 No authentication, so it is insecure
NFS (Network File System):
 NFS is a jewel of protocol for file transfer
 If NT is the Server and Unix client login into the NT then NT use the portion of RAM on
NT server to transparently store the Unix file so that Unix user can use the file it
format
 Unix user and NT user can access the file in their normal file system
SMTP (Simple Mail Transfer Protocol):
 SMTP use to send mail and POP3 use to receive the mail
 Uses spooled or queued, method of mail delivery

5.  Once the message is sent to destination then mail are spooled to a device-disk and
regularly check the queue for message, if destination found then sends to it
LPD (Line Printer Daemon):
 LPD design for Printer Sharing
 LPD with LPR (Line Printer) allow to spool and sent to network printer using TCP/IP
X Window:
 Design for client/server operation
 It define a protocol to design client/server application on GUI
 The idea is to allow program called client to rum computer on Server
SNMP (Simple Network Management):
 Collect and manipulate network information
 This protocol can also stand as watchdog over the network, quickly notifying manager
of any sudden change of event into network
 This also called as agent, when aberration occur
DNS (Domain Name System):
 DNS resolve host name – specifically, internet name such as www.vikk.com
 If you don’t have DNS then you type IP address to communicate with other
 DNS allow to use domain name to specify an IP address, and can change IP address no
one will know the difference
 DNS is use to resolve FQDN (Fully Qualified Domain Name) such as www.vik.king.com.
DHCP (Dynamic Host Configuring Protocol):
 DHCP assign IP address to Host
 All type of devices can be use for DHCP even Cisco Router
 There is lots of information provided by DHCP if host requesting to DHCP and that are
o IP address
o Subnetmask
o Domain name
o Default gateway
o DNS
o WINS information

6.  A client sends out a DHCP discover message in order to get IP address send an
broadcast at layer 2 and layer 3. Layer 2 broadcast look like FF:FF:FF:FF:FF:FF and layer
3 uses 255.255.255.255
 Broadcast saying “Help-I don’t know my IP”
 DHCP uses UDP (User Datagram Protocol) at transport layer
TCP (Transmission Control Protocol):
 TCP takes large block of information from application and breaks is into Segment
 It numbers and sequences each segment so that destination TCP can put back in order
 After this segment are sent, TCP wait for Acknowledge
 The sender TCP stack contact destination TCP stacks to establish the connection, what
is crated is known as Virtual Circuit.
 This type of Communication is called Connection Oriented
 During the initial handshake, two TCP also agree on the amount of information that
going to transfer
 TCP is full-duplex, Connection oriented, reliable transfer
 TCP Segment format:
o The TCP create lots of Overhead, to save this overhead there also one option is
available i.e. UDP.
Fig.: TCP Segment Format
UDP (User Datagram Protocol):
 UDP is connectionless service therefore doesn’t create virtual circuit
 Less overhead, But unreliable transfer

7.  Doesn’t sequence the segments
Fig.: UDP segment format
Some Key feature of TCP and UDP:
CDP (Cisco Discovery Protocol):
 The best way to built and troubleshoot network is CDP
 CDP is Cisco Proprietary protocol design to help administrators collect information
about both locally attach and remote devices
 We can gather hardware & protocol information of neighbor device

8. Fig.: CDP’s CLI snap shot
Protocol Port No.
20 FTP data (File Transfer Protocol)
21 FTP (File Transfer Protocol)

9. 22 SSH (Secure Shell)
23 Telnet
25 SMTP (Send Mail Transfer Protocol)
43 whois
53 DNS (Domain Name Service)
68 DHCP (Dynamic Host Control Protocol)
79 Finger
80 HTTP (HyperText Transfer Protocol)
110 POP3 (Post Office Protocol, version 3)
115 SFTP (Secure File Transfer Protocol)
119 NNTP (Network New Transfer Protocol)
123 NTP (Network Time Protocol)
137 NetBIOS-ns
138 NetBIOS-dgm
139 NetBIOS
143 IMAP (In ternet Message Access Protocol)
161 SNMP (Simple Network Management Protocol)
194 IRC (Internet Relay Chat)
220 IMAP3 (Internet Message Access Protocol 3)
389 LDAP (Lightweight Directory Access Protocol)
443 SSL (Secure Socket Layer)
445 SMB (NetBIOS over TCP)
666 Doom
993 SIMAP (Secure Internet Message Access Protocol)
995 SPOP (Secure Post Office Protocol)
OSI Reference Model
OSI (Open System Interconnection):
 OSI is published by ISO (International Organization for Standardization) in late 1984’s

10.  This is design to help Vendor to create interoperable devices in a market
 It describes how data and network information are communicated from an application
on one computer through the network media to an application on another computer
 The OSI reference model breaks this communication approach intolayers so it is a
layer based model.
 OSI is a set of guideline that application programmercan use to implement and
develop the networking standard
 OSI having 7 layers out of which top 3 layer define how the application within end
station will communicate with each other and with user. Other 4 layer define how
data is transmitted from end to end.
 OSI have connectionless & connection oriented in Network Layer
 But have only connection oriented in Transport Layer
Fig.: OSI reference model and their functions

11. Port no. at transport layeris use by Host to create session with other host in form of Virtual
Circuit
Fig.: Port number at Transport Layer
LAN (Local Area Network)
Ping (Packet InterNet Groper):
 Use ICMP echo request and replies to test if a node IP stack is initialize and alive on
the network

12. Traceroute:
 Display the list of router on a path to network destination, This will not working with
DOS
 Tracert: Same as traceroute but it is work in DOS
Arp (Address Resolution Pointer):
 Display IP to MAC address mappings on a Window PC
CSMA/CD (Carrier Sense Multiple Access with Collision Detection):
 CSMA/CD is a protocol which helps device toshare bandwidth equally and sense
collision
 If host detect another signal then it sends a jam signals inform other devices that a
collision occur
 Each device on Ethernet segment stops transmitting for period of time
 If collisions keep occurring after 15 tries, the nodes attempting to transmit will then
timeout.
Half Duplex Full Duplex
 Collision will occur because single wire
is used
 No collision will occur because
multiple wire use to send and receive

13.  Typically 10Base T- only 30 to 40
percent efficient
 We can use it for Hub
 100 percent efficient
 We can not use it with Hub
LAN traffic cause:
 Too many host in the broadcast domain
 Broadcast storm
 Multicasting
 Low Bandwidth
WAN (Wide Area Network)
CPE (Customer Premises Equipment):
 Equipment owned by subscriber and located into subscriberpremises
Demarcation (Boundary Area) Point:
 This is a service provider end point, from this CPE start
 It is owned and installed by ISP, It is usually connection toCSU/DSU or ISDN interface
Local Loop:
 Local loop connect the Dmarc to closet switching office

14. Central Office:
 This connect the customer network with ISP’s switching network
DCE (data circuit-terminating equipment):
 is a device that sits between the data terminal equipment (DTE) and a data
transmission circuit.
 In a data station, the DCE performs functions such as signal conversion, coding, and
line clocking and may be a part of the DTE or intermediate equipment.
DTE (Data Terminating Equipment):
 device is the terminal (or computer)
Fig.: WAN Connection type
Lease Line:
 Point to Point dedicated connection
 Pre-established WAN communication path that goes from the CPE through DCE switch
 It synchronies serial line up to 45Mbps
 HDLC and PPP are frequently use in Lease Line
Circuit Switch:

15.  Circuit Switching support only phone call
 We pay it when we use it for phone call
 It use Dial-Up or ISDN and is use for low bandwidth
Packet Switching:
 This is WAN technology can share bandwidth other company to save money
 Packet switching are only workfor you if data is burst type-not continuous
 Frame relay and X.25 are packet switching technology that can range from 56Kbps to
T3 (45Mbps).
Dial-Up:
 Dial-up internet access is a form of internet access that use the facility of PSTN to
establish dialed connection to an ISP via telephone line
 User’s computer or router use modem to encode and decode Internet protocol packet
and control information into and from analogue audio frequency signal
Fig.: Dial-up Connection using modem
MPLS (Multiprotocol Label Switching):
 MPLS using both Packet and Circuit switching technology
 High-Performance telecommunication network
 MPLS is a switching mechanism that imposes label on packet toforward
Frame-Relay:
 Frame-relay is high-performance Data Link and Physical Layer specification

16.  This is more cost effective than point-to-point link, run at speed of 64Kbps to 45Mbps
 It provide feature of dynamic bandwidth allocation and congestion control
LAPB (Link Access Procedure):
 Link Access Procedure, Balance was created connection oriented protocol at data link
layer use with X.25
LAPD (Link Access Procedure):
 Link Access Procedure, D-Channel is used with ISDN at the data link layer as a protocol
for D channel
HDLC (High Level Data Link Control):
 HDLC is bit-oriented synchronous data linkprotocol
 HDLC can be use for point to multipoint connection , but is now used exclusively to
connect one device with another
 Each vendor’s HDLC is proprietary with regards to specific equipment because HDLC
header’s doesn’t contain any identification about the type of protocol being carried
inside HDLC encapsulation. (Not necessary as Network layerprotocol - IP)
PPP (Point-to-Point Protocol):
 PPP is pretty famous than HDLC because all multiport version of HDLC are proprietary
and PPP can use to create point to point links between multivendor equipments
PPPoE (Point-to-Point over Ethernet):
 Use to encapsulate PPP frame into Ethernet frame
 It gives you lot of PPP feature like Authentication, Encryption and Compression
 PPPoE on Ethernet’s main feature that it adds direct connection to Ethernet interfaces
while providing DSL (Digital Subscriber Line).
DSL (Digital Subscriber Line):
 DSL is use by traditional telephone companies to delivers advanced services (High
Speed Data and some time Video)
 It typically has lower data carrying capacity than HFC (Hybrid fiber-coaxial)
 Data speed is depend on line length and Quality

17.  DSL connection are employed in last mile of local telephone network, the connection
is setup between either end of copper wire that run between CPE and DSLAM (Digital
Subscriber line access multiplexer)
 IN SDSL (Symmetric Digital subscriber Line), Upstream and Downstream are same
HFC (Hybrid Fiber-coaxial):
 HFC is telecommunication term for broadband network, which combine optical fiber
and coaxial cable
 It has commonly employed globally by cable television operator
ATM (Asynchronous Transfer Mode):
 Is created for time sensitive traffic, provide simultaneous transmission of Voice, Video
and Data
 ATM cell of 53 byte long instead of Packet
 It use isochronous clocking to help tomove data faster
Media, Cable, Port
Cable:
 EIA/TIA (Electronic Industries Association/Telecommunication Industry Alliance) is the
standard body that creates the physical layer specification for Ethernet.
 Have inherent attenuation (Loss of signal strength due length) measured in db
(decibel)
 Higher quality cable has high rated categories and low attenuation.
 Cat5 has less crosstalk (unwanted signal interference) than cat3 cable.
 IEEE 802.3 standards:
o 10Base2 (10=10Mbps, Base=Baseband, 2=almost 200 meter):
 10Mbps, Base band technology
 185 Meter in length
 Known as “Thinnet” support up to 30 workstation
o 10Base5 (10=10Mbps, Base=Baseband, 5=almost 500 meter):
 Known as “Thiknet”.
 Use up to 2500 meter with repeater and 1024 user for all segment
o 10BaseT:
 10Mbps with Cat 3 UTP like 10Base2 and 10Base5
 4 pair UTP
o AUI (attachment Unit Interface):

18.  802.3 define AUI which allow 1 bit at a time transfer to physical Layer
from the data link media access
 It allow MAC to remain constant but physical layer can support any
existing new technology
 Original AUI is 15 pin connector, which have transceiver which convert
15 pin-to-twisted pair
 AUI cannot support 100Mbps because of high frequency
o MII (Media Independent Interface):
 802.3u specification created one called MII
 MII provide 100Mbps throughput
 The MII uses 4 bit called nibble, and transmit 8 bit at a time
 802.3u (fast Ethernet) support 802.3 because they share physical layer
 Expanded IEEE 802.3 standard:
o 100BaseTX (IEEE 802.3u):
 5,6 and 7 cat UTP two-pair wiring, 100 meter, use RJ45(Registered Jack
4 5)
o 100BaseFX (IEEE 802.3u):
 Use fiber cabling 62.5/125 micron fiber cable
 Support point-to-point topology and 412 meter long distance
o 10000BaseCX (IEEE 802.3z):
 Copper twisted pair cable called twinex run only 25 meter
o 1000BaseSX (IEEE 802.3z):
 62.5 and 50 micron can go up to 250 meter with 62.5 and 550 with 50
micron
o 1000BaseLX (IEEE 802.3z):
 9 micron run up to 3 kilometer to 10 kilometer
Straight Through Cable:

19. Usedbetween:
 Host to Hub, Switch
 Router to Hub, Switch
Crossover Cable:
Usedbetween:
 Host to Host, Router
 Switch to Switch, Hub
 Router to Router
Rolled Cable:
 Rolled cable is to connect Host and Router serial communication port

20. MAC (Media Access Control):
 MAC is 48-bit (6-byte) physical address to the Host, it is burnt into NIC (Network
Interfacing Cart) by Manufacturer
 MAC is unique code, written in hexadecimalformat, which is divided as
Fig.: MAC Address format
 If G/L (Global/Local Bit) it 0 the Globally assigned if 1 then local assigned
 I/G (Individual/Group) if 0 then Source portion of MAC, if 1 then represent broadcast
or multicast address in Ethernet
Ethernet Frame:
 Encapsulating a frame into different type of frame is called tunneling
VLAN (Virtual Local Area Network)
 VLAN create a single set of domain
 VLAN Segments the broadcast domain into many segment
 Generally to divide the broadcast domain we required Router, but using VLAN we can
separate or segment the LAN in single device (Switch).

21.  The User’s wants security then we can create their own VLAN, and other user cannot
access them in single switch. So VLAN enhance the network security.
 By default switch have VLAN 1 (1 is ID) this ID is of 12bit, 212=4096 ID’s
 ID from 1-1005 are normal range, ID from 1006-4094 are Extended range
 ID from 1002-1005 are already available in every switch
 So we started with 2 – 1001 (Example: VLAN 2, VLAN 3,………, VLAN 1000, VLAN 1001)
 Host in VLAN can communicate with other in same VLAN.
 If we need inter VLAN communication then we need router or VTP.
 Feature of VLAN:
o Broadcast Control
o Security
o Flexibility and Scalability
Fig.: Switches Created the Physical boundaries
 VLAN configuration:

22. VTP (VLAN Trunking Protocol)
 Basic concept of VTP is to manage all configured VLAN’s and to maintain consistency
throughout the network
 VTP is use to delete, add and rename the VLAN
 Accurate tracking and monitoring
 VTP provide plug and play VLAN
 VTP only manage normal – range VLAN (1 to 1005), the switch must be in transparent
mode if they are in extended – range (1006 to 4094)
 To manage VTP we have to create one Switch as Server and other as a domain so that
Server can share VLAN information to other domain via trunk port (we have to create
trunk port in all switch by which they are connect toeach other)
 Modes of Operation:
o Server Mode:
 This is the default mode of all catalyst switches.
 One of switch must operate into server mode; Server switch can create,
add and delete VLAN and VTP domain.
 Configuration saves into NVRAM.
o Client Mode:
 The switch working in client mode can receive information from VTP
server
 Client switch cannot create, add and delete the VLAN
 Configuration not saves in NVRAM.
o Transparent Mode:

23.  Then can add, delete and create VLAN because they keep information
by their own database
 Basically the transparent mode allows remote switches to share VLAN
information those are not within the same VLAN.
Fig.: Modes of VTP
 Configuration:
o To share information they must have same password
o VTP management domain name must to be same, and one of the switch as
Server
Fig.: VTP simulation

24. Switch Port Interface
 Switchport mode access:
o Keep the port in permanent nontrunking mode
o The interface become nontrunking regardless of neighboring interface in trunk
mode
 Switchport mode dynamic auto:
o This makes the interface able to convert into trunking mode
o If neighbor interface is in trunk mode then it will change
 Switchport mode dynamic desirable:
o The interface become a trunk interface if the neighborinterface is trunk
 Switch port mode trunk:
o Keeps the interface into trunk mode whether neighboring interface is in trunk
 Switchport nonegotiate:
o We can use this command only when port is in access or trunk
 Adding and deleting VLAN:
Case1
Case2
Case3
Case4
Case5 for Native trunk

25.  Inter VLAN routing
Fig.: Inter VLAN routing
Port Security:
IP Addressing

26.  IP address is logical address given to the software where as MAC address is physical
address given to the hardware.
 32 bit address scheme is used in a network, so we can have 232=4,29,49,67,296
address
Network Address:
 Network address looks like 10.0.0.0, 172.16.0.0, 192.168.1.0
Host Address:
 Host address looks like 10.10.10.10, 172.16.1.1, 192.168.1.1
Broadcast:
 Broadcast address is used by application or host to send information to all hosts in a
network.
 255.255.255.255 it means all network, 10.255.255.255 means all host of network 10.
Class of IP address:
Class A address:

Routing & Routing Protocol
Routing: It is the process of selecting path in a network for sending traffic. There are two
type of routing
 Static Routing :
o It uses the path which network administrator manually configure in the router
o Topology change required manual update
o Allows precise control over routing behavior
 Dynamic Routing:
o Use a route that a network routing protocol adjust automatically for topology

27. o Router learn and maintain routes by exchanging routing update
o Router able to discover new network by sharing the routing table
Routing Protocol: Routing protocol is a protocol that specifies how router will
communicate with each other.
Three type of Routing Protocol;
 Interior gateway routing via Link state routing protocol
o OSPF (Open Shorted Path First)
o IS-IS (Intermediate System to Intermediate System )
 Interior gateway routing via Distance Vector
o RIP (Routing Information Protocol)
o IGRP (Interior Gateway Routing Protocol)
o EIGRP (Enhance Interior Gateway Routing Protocol)
 Exterior Gateway Routing Protocol
o BGP (Border Gateway Protocol)
Administrative Difference:
 Administrative difference is the feature that router use to select best path when there
are two or more different routes to the same destination from two different routing
protocols. Administrative distance defines the reliability of a routing protocol. Each
routing protocol is prioritized in order of most to least reliable (believable) with the
help of an administrative distance value.

28. RIP (Routing Information Protocol):
 There are two version of RIP i.e. RIPv1 and RIPv2
 Metric (standard of measurement) is hope count
 AD is 120 it using bellman ford algorithm to fine the best path
 It support auto summarization
 RIP work up to 16 hope count
 16th hope count is poisonous hope count means dead
 If router sends it information with hope count 16 then it is dead and is called route
poisoning
 Split Horizon: In this router sends the information to other router by interface is not
duplicate with other interface.
 Hold Down Process: If router R1 sends ACK with hope count 16 then router R3
understand that R1 is dead and it keep the detail of R1 for 180 Sec. this is call HDT
 Flush Timer: After every 30 Sec. if R1 again sending dead then flush timer start and it
flush the information of R1 from routing table.

29. Classful: Router doesn’t send subnet mask. It works on default class subnet mask. In IPv4
class A, B and C are called class full network, because these network are define by class rule
for IPv4 addressing.
Classful Routing Protocol: Does not transmit the mask the mask information along
with subnet number. And therefore must consider class A, B and C Class boundaries and
perform auto summarization at those boundaries.
Classless Routing Protocol: It sends subnet mask in its routing updates
OSPF (Open Shortest Path First):
 OSPF is open standard routing protocol
 It crate three table
o Routing table
o Topology table
o Neighbor table
 AD is 110
 It uses Dijikstra algorithm
 Hello timer of OSPF is 10 sec.
 Dead timer is 40 sec
 It support manual summarization
 It support two type of authentication
o Pain Text
o MD5 (Message Digest ) Fig.: Hello Timer
EIGRP (Enhance Interior Gateway Routing Protocol):
 It is Cisco propriety routing protocol
 AD is 90
 It classless routing protocol, support for VLSM

30.  Create three routing table
o Neighbor Table
o Routing Table
o Topology Table
 It uses composite metric, which is calculated by 5 parameter
o Bandwidth
o Delay
o Load
o Reliability
o Maximum transmission unit
 It uses dual algorithm to find best path
 It uses multicast IP address 224.0.0.10
 It support only MD5 authentication
 It support equal and unequal cost load balancing