CCNA, IIHT , Hudson lines
Submitted for the partial fulfillment of
Bachelor of technology
E .C . E
Submitted By :TALVINDER SINGH (04013202810)
4th year , E.C.E-1
Guru TeghBahadur Institute of Technology,
Guru Gobind Singh Indraprastha University
Sector-16 Dwarka , New delhi
I take this opportunity to express my profound gratitude and deep regards to my guide
(kalyansingh/GTBIT) for his exemplary guidance, monitoring and constant
encouragement throughout the course of this thesis. The blessing, help and guidance
given by him time to time shall carry me a long way in the journey of life on which I am
about to embark.
I also take this opportunity to express a deep sense of gratitude to Er. Naveen
Bansal&Vinaykohli ,IIHT, for cordial support, valuable information and guidance, which
helped me in completing this task through various stages.
I am obliged to staff members of IIHT, for the valuable information provided by them in
their respective fields. I am grateful for their cooperation during the period of my
Lastly, I thank almighty, my parents, brother and teachers for their constant
encouragement without which this assignment would not be possible.
About the Institute
IIHT is Asia's No. 1 IT training organization with more than 200 centres in the country and
presence in more than 17 countries worldwide. IIHT, over the years, has mastered the training
delivery process and its flair for imparting education is impeccable. Also, IIHT has successfully
maintained standards in terms of ambience, infrastructure and courseware across all its centres.
Vision - To provide high quality IT training services at an international level reaching out to
IIHT Cisco Training Courses
Cisco is a leading provider of IT products and services that ensures business benefits and helps in
overcoming various IT challenges. Cisco also offers a variety of certification programs for
professionals, employees and students. Cisco offers five levels of IT certification with eight
different career paths including routing and switching, design, network security, service
provider, service provider operations, storage networking, voice and wireless. The five levels of
Cisco certification are Entry, Associate, Professional, Expert and Architect. Cisco certification is
one of the most demanded technology certifications in the global job market. IIHT offers Cisco
training courses for CCNA, CCNP and CCIE.
A JOURNEY TOWARDS CISCO-CERTIFIED NETWORK ASSOCIATION (CCNA)
Candidates have the option of gaining the certification by passing two tests (ICNDI 640-822 and ICND2 640-816), or
one single test (CCNA 640-802); the two-test option has the advantage of allowing the candidate to focus on
The certification is valid for three years; at the time a CCNA holder must either re-take the CCNA or ICND exam, or
take and pass an exam for one of the Professional (e.g., CCNP) or Specialist level; certifications (excluding the sales
specialist exam), or pass the CCIE written exam.
These exams are known by their corresponding numbers. When the curriculum of the exam changes the exam
number also changes. The current exam number for CCNA is 640-802 (from 15 Aug 2007). New ICND Part 1 (640822 ICND1) and ICND Part 2 (640-816 ICND2) are available from 15 Aug 2007. Part 1 by itself will give you a CCENT.
These exams are conducted by authorized test centers at a cost of $125 USD each for the ICND1 or ICND2 exams
and $150 USD for the full CCNA exam..
Cisco Systems, Inc is a multinational corporation with more than 63,000 employees and annual revenue of US$35
billion as of 2007. Headquartered in San Jose, California, it designs and sells networking and communications
technology and services under five brands, namely Cisco, Linksys, WebEx, IronPort, and Scientific Atlanta.
CCNA was launched by CISCO SYSTEMS. It stands for CISCO CERTIFIED NETWORK ASSOCIATE. CISCO has 37%
market shares in internetworking devices. Hence, when we study and complete CCNA certification you are
recognized internationally. CCNA is recognized all over the world and prepares you for carrier that spans all over
INTERNETWORKING BASIC & DEVICES.
Internetworking involves connecting two or more distinct computer networks or network segments together to
form an internetwork (often shortened to internet), using devices which operate at layer 3 (Network layer) of the
OSI Basic Reference Model (such as routers or layer 3 switches) to connect them together to allow traffic to flow
back and forth between them. The layer 3 routing devices guide traffic on the correct path (among several
different ones available) across the complete internetwork to their destination.
The Basic LAN (Figure 1b)
JON starts with converting name to its corresponding IP address using Name resolution technique; generally it
involves the DNS or WINS.
Here is the output cut how resolution process going on, when JON sends the data to LIN’s computer.
To overcome the LAN traffic congestion, a large network is segmented into some bunch of smaller networks which
is called segmentation. Segmentation is done using Switches. A Switch has multiple collision domains and single
broadcast domains, or a Router, which has multiple collision domains as well as multiple broadcast domains. The
figure below, fig. 1c, displays a network that is segmented using a switch. It now separates the collision domain
which is not done by HUB in figure 1b.
A switch replaced by HUB to break the collision domain (Figure 1c)
Large number of hosts in a single broadcast domain
Using HUB for connectivity
A bundle of name resolution and address alteration traffic like ARP or IPX.
In the above discussion we have dealt with how to minimize the LAN congestion. Now it’s time to minimize the
broadcast storming occurring at WAN links or, better to say, splitting the broadcast domain. The broadcast domain
can be split by the router, because routers have the following advantage:
Router don’t forward broadcast by default.
Router can filter the data packets depending upon the Layer 3 (i.e. Network Layer) information (i.e. IP
The functions which are done by the router in an internetwork are mentioned below …
Remember that routers are really switches but better to say that they are actually layer 3 switches. Router will
forward data packets or frames depending upon the IP address, which is called packet switching.
Let’s conclude about collision domain and broadcast domain…
Collision: The effect of two nodes sending transmissions simultaneously in Ethernet. When they meet on the
physical media, the frames from each node collide and are damaged.
Collision Domain: The network area in Ethernet over which frames that have collided will be detected. Collisions
are propagated by HUBS and Repeaters, but not by LAN switches, routers or bridges.
Broadcast: A data frame or packet that is transmitted to every node on the local network segment. Broadcasts are
known by their broadcast address, which is a destination network and host address with all the bits turned ON.
Broadcast Domain: A group of devices receiving broadcast frames initiating from any device within the group.
Because routers don’t forward broadcast frames, broadcast domains are not forwarded from one broadcast to
OPEN SYSTEM INTERCONNECTION REFERENCE MODEL
The Open System Interconnection (OSI) reference model describes how information from a software application in
one computer moves through a network medium to a software application in another computer. The OSI
reference model is a conceptual model composed of seven layers, each specifying particular network functions.
The model was developed by the International Organization for Standardization (ISO) in 1984, and it is now
considered the primary architectural model for inter-computer communications.
Characteristics of the OSI Layers:
The seven layers of the OSI reference model can be divided into two categories: upper layers and lower layers.
The upper layer of the OSI model deal with application issues and generally are implemented only in software. The
lower layers of the OSI model handle data transport issue. The physical layer and the data link layer are
implemented in hardware and software.
The OSI model provides a conceptual framework for communication between computers, but the model itself is
not a method of communication. Actual communication is made possible by using communication protocols. In the
context of data networking, a protocol is a formal set of rules and conventions that governs how computers
exchange information over a network medium.
The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating
maintaining, and deactivating the physical link between communicating network systems. Physical layer
specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum
transmission distances, and physical connectors.
Data Link Layer:
The data link layer provides reliable transit of data across a physical network link. Different data link layer
specifications define different network and protocol characteristics, including physical addressing, network
topology, error notification, sequencing of frames, and flow control. Physical addressing (as opposed to network
addressing) defines how devices are addressed at the data link layer. Network topology consists of the data link
layer specifications that often define how devices are to be physically connected, such as in a bus or a ring
topology. Error notification alerts upper-layer protocols that a transmission error has occurred, and the sequencing
of data frames recorders frames that are transmitted out of sequence.
The Logical Link Control (LLC) sublayer of the data link layer manages communications between devices over a
single link of a network. LLC is defined in the IEEE 802.2 specification and supports both connectionless and
connection-oriented services used by higher-layer protocols. IEE 802.2 defines a number of fields in data link layer
frames that enable multiple high-layer protocols to share a single physical data link. The Media Access Control
(MAC) sublayerof the data link layer manages protocol access to the physical network medium.
Media Access Control (MAC) addresses consist of a subset of data layer addresses. MAC addresses identify
network entities in LANs that implement the IEEE MAC addresses of the data link layer. As with most data-link
addresses, MAC addresses are unique for each LAN interface.
Mac Addresses, Data-Link Addresses, and the IEET Sublayers of the
Data Link Layer Are All Related (Figure 1k)
Mac addresses are 46 bits in length and are expressed as 12 hexadecimal digits. The first 6 hexadecimal digits,
which are administrated by the IEEE, identify the manufacturer or vendor and thus comprise the Organizationally
Unique Identifier (OUI). The last 6 hexadecimal digits comprise the interface serial number, or another value
administered by the specific vendor.
Because internetworks generally use network addresses to route traffic around the network, there is a need to
map network addresses to MAC addresses. Different protocol suites use different methods for determining the
MAC address of a device. The following three methods are used most often. Address Resolution Protocol (ARP)
maps network addresses to MAC addresses. Address Resolution Protocol (ARP) is the method used I the TCP / IP
suite. When a network device needs to send data to another device on the same network, it knows the source and
destination network addresses for the data transfer.
The network layer defines the network address, which differs from the MAC address. Some network layer
implementations, such as the Internet Protocol (IP), define network addresses in a way that route section can be
determined systematically by comparing the source network address with the destination network address and
applying the subnet mask. Because this layer defines the logical network layout, routers can use this layer to
determine how to forward packets.
The transport layer accepts data from the session layer and segments the data for transport across the network.
Generally, the transport layer is responsible for making sure that the data us delivered error-free and in the proper
sequence. Flow control generally occurs at the transport layer. Flow control manages data transmission between
devices so that the transmitting device does not send more data than the receiving device can process.
Flow control is a function that prevents network congestion by ensuring that transmitting devices do not
overwhelm receiving devices with data. A high-speed computer, for example, may generate traffic faster than the
network can transfer it, or faster than the destination device can receive and process it. The three commonly used
methods for handling network congestion are buffering, transmitting source-quench message, and windowing.
Buffering is used by network devices to temporarily store bursts of excess data in memory until they can be
processed. Occasional data bursts are easily handled by buffering. Excess data brusts can exhaust memory,
however, forcing the device to discard any additional datagram’s that arrive.
The session layer establishes, manages, and terminates communication sessions. Communication sessions consist
of service requests and service responses that occur between applications located in different network devices.
These requests and responses are coordinated by protocols implemented at the session layer.
The presentation layer provides a variety of coding and conversion functions that are applied to application layer
data. These functions ensure that information sent from the application layer of one system would be readable by
the application layer of another system. Some examples of presentation layer coding and conversion schemes
include common data representation formats, conversion of character representation formats, common data
compression schemes, and common data encryption schemes.
The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and
the user interact directly with the software application.
This layer interacts with software applications that implement a communicating component. Such application
programs fall outside the scope of the OSI model. Application layer functions typically include identifying
communication partners, determining resource availability, and synchronizing communication.
The sending and receiving of data from a source device to the destination device is possible with the help of
networking protocols by using data encapsulation. The data is encapsulated with protocol information at each
layer of the OSI reference model when a host transmits data to another device across a network.
Protocol Data Unit (PDU):
The Protocol Data Units contain the control information attached to the data at each layer. The information is
attached to the header of the data field but can also be in end of the data field or trailer. PDUs are encapsulating
by attached them to the data at each layer of the OSI reference model.
Encapsulation and De-Encapsulation Process:
The encapsulation and de-encapsulation of header control information on each layer of the OSI reference model is
The data encapsulation process is defined as below:
TCP Header Encapsulation:
The application-layers user data is converted for transmission on the network. The data stream is the handed
down to the transport layer, which sets up a virtual circuit to the destination. The data stream is then broken up,
and a Transport layer header is created and called a segment. The header control information is attached to the
Transport layer header of the data field. Each segment is sequenced so that data stream can be put back together
on the destination exactly as transmitted.
IP Header Encapsulation:
Each segment is then handed to the Network layer for logical addressing and routing through a routed protocol,
for example, IP, IPX, Apple Talk and DECNET etc. the Network-layer protocol adds a header to the segment handed
down to the Data link layer. Remember that the 3 and 4 layers work together to rebuild a data stream on a
Mac Header Encapsulation:
The Data Link layer receives the packets from the Network layer and placing them on the network medium such as
cable or wireless media. The Data Link layer encapsulates each packet in a frame, and the MAC header carries the
source Mac address and destination Mac address.
Physical Layer Encapsulation:
Once the frame gets to the destination network, a new frame is used to get the packet to the destination host. To
put this frame on the network, it must first be put into a digital signal.
On destination side, the receiving devices will synchronize on the digital signal and extract the 1s and 0s from the
digital signal. At this point the devices build the frames, run a Cyclic Redundancy Check (CRC), and then check their
output against the output in the Frame Check Sequence (FCS) field of the data frame. If the information matches
then the packed is pulled from the frame, and the frame is discarded. This process is known as de-encapsulation
Ethernet cabling is an important discussion, especially if you are planning on taking the Cisco exams. Three types of
Ethernet cables are available:
Straight Through Cable:
In case of straight through cable the 8 wires of cat 5 or cat 6 are connected with Rj45 connectrors serially means 1
The straight through cable is used to connect
Host to switch or hub
Router to switch or hub.
Means we can say straight through cable is used to connect different devices, the only exception is that, if router’s
Ethernet port is directly connected with computer Ethernet port. Four wires are used in straight through cable to
connect Ethernet devices.
Cross Over Cable:
The cross over cable is used to connect same device, like…
Switch to Switch
Hub to Hub
Hub to Switch
Router Direct to Computer
Computer to Computer
The same wires (like 184.108.40.206.) are used in this cable as in the straight through cable; we just connect different pins
Rolled Over Cable
Although rolled over cable isn’t used to connect any Ethernet connections together, you can use a rolled over
Ethernet cable to connect a host to a router console serial communication port.
If you have a Cisco Router or Switch, you would use this cable to connect your PC running HyperTerminal to the
Straight Though Cable Pin Out for T568A:
Rj45 Pin #
Cross Over Cable (T568B):
Rj45 Pin #
The first thing that you’ll notice when you pull a Cisco 2500 series router out of the box is obviously its physical
elements. A Cisco 2501 includes not only Ethernet and serial ports, but also console and auxiliary ports. In this
section we’ll look at the purpose of each, their physical characteristics and how devices are attached and cabled.
Note that hardware ports are numbered nominally starting at 0. Therefore on a system with only one Ethernet
port, that port is referred to as Ethernet 0.
ETHERNET PORT AND CONNECTOR WITH CABLE
A Cisco 2501 includes a single 10Mb Ethernet port. While many Cisco router models now include an integrated
10/100 Rj-45 port, the 2500 series uses what is referred to as a generic attachment unit interface (AUI) DB-15 port
instead. The name of this connector (DB-15) comes from the fact that it is physically shaped like the letter ‘D’ and
uses a 15-pin connector.
SERIALPORT AND CONNECTOR WITH CABLE
A variety of Physical Layer standards are supported over synchronous serial interfaces to connect to different types
of DCE equipment. Some of the different signaling standards and connectors that might be found on DCE
equipment include EIA/TIA-232, EIA/TIA-449, V.35, X.21, and EIA-530. Cisco and a variety of other vendors
manufacturer “transition” cables capable of connecting a router’s DB-60 DTE port to DCE equipment using these
ARCHITECTURE OF TCP/IP MODEL
An architectural model provides a common frame of reference for discussing Internet communications. It is used
not only to explain communication protocols but to develop them as well. It separates the functions performed by
communication protocols into manageable layers stacked on top of each other. Each layer in the stack performs a
specific function in the process of communicating over a network.
Generally, TCP/IP is described using three to five functional layers. To describe TCP/IP based firewalls more
precisely, we have chosen the common DoD reference model, which is also known as the Internet reference
The Application layer consists of application programs
and serves as the windows, or network interface. It is
through this window that all exchange of meaningful
information occurs between communication users.
Examples include Telnet and SMTP.
Provides end-to-end data delivery services. The
protocols at this layer are TCP and UDP.
Host-to-Host Transport Layer
Defines the datagram or frame format and handles
routing data through an internetwork. Examples include
IP and ICMP.
Defines how to access a specific network topology such
as Ethernet or Token-Ring.
Network Access Layer
SourcePort: The 16-but port number of the process that originated
the TCP segment on the source device. This will normally be an
ephemeral (client) port number for a request sent by a client to a
server, or a well-known/registered (server) port number for a reply
from a server to a client.
DestinationPort: The 16-bit port number of the process that is the
ultimate intended recipient of the message on the destination
device. This will usually be a well-known / registered (server) port
number for a client request, or an ephemeral (client) port number for
a server reply.
Sequence Number: For normal transmissions, the sequence number
of the first byte of data in this segment. In a connection request
(SYN) message, this carries the initial sequence number (ISN) of the
source TCP. The first byte of data will be given the next sequence
number after the contents of this field, as described in the topic on
sequence number synchronization.
Acknowledgement Number: When the ACK bit is set, this segment
Number is serving as an acknowledgement (in addition to other
possible duties) and this field contains the sequence number the
source is next expecting the destination to send. See the topic
describing TCP data transfer for details.
Data Offset: Specifies the number of 32-bit words of data in the TCP
header. In other words, this value times four equals the number of
bytes in the header, which must always be a multiple of four. It is
called a “data offset” since it indicates by how many 32-bit words the
start of the data is offset from the beginning of the TCP segment.
Reserved: 6 bits reserved for future use; sent as zero.
Control Bits: As mentioned, TCP does not use a separate format for
control messages instead certain hits are sent to indicate the
communication of control information.
Windows: Indicates the number of octets of data the sender of this
segment is willing to accept from the receiver at one time. This
normal corresponds to the current size of the buffer allocated to
accept data for this connection. This field is, in other words, the
current receive window size for the device sending this segment. See
the data transfer mechanics topic for details.
Checksum: A, 16 nit checksum for data integrity protection
computed over the entire TCP datagram plus a special “pseudo
header” of fields. It is used to protect the entire TCP segment against
not just errors in transmission, but also errors in delivery. Optional
alternate checksum methods are also supported.
Urgent Pointer: Used in conjunction with the URG control bit for
priority data transfer. This field contains the sequence number of the
last byte of urgent data. See the priority data transfer topic for
Options: TCP includes a generic mechanism for including one or
more sets of optional data in a TCP segment. Each of the options can
be either one byte in length or variable in length. The first byte is the
Option-Length: The length of
the entire option in bytes,
including the Option-Kind and
Option-Data: The option data
itself in at least one oddball
case, this fields omitted (making
Option-Length equal to 2)
Padding: If the Option field is not a multiple 0f 32 bits in length
enough zeroes are added to pad the header so it is a multiple of 32
Data: The bytes of data being sent in the segment.
TCP/IP ENCAPSULATION AND DECAPSULATION:
Encapsulation is used to isolate each of the layers in the protocol stack. Each layer frames the data prepending the
data with its own header information. In the sending machine, the layer places its own header information in front
of the data it gets from the layer above before passing it to the layer below. In the receiving machine, each layer
first interprets and then strips the header information from frames received from the layer below before passing
them up to the layer above. In reality it is not quite so simple.
Internet Protocol (IP) Technology was developed in the 1970s to support some of the first research computer
networks. Today, IP has become a worldwide standard for home and business networking as well. Our network
routers, Web browsers, email programs, instant messaging software – all rely on IP or other network protocols
layered on top of IP.
IPv4 uses 32-bit (four type) addresses, which limits the address space to 4,294,967,296 (2 ) possible unique
addresses. However, some are reserved for special purposes such as private networks (~ 18 million addresses) or
multicast addresses (~ 16 million addresses). This reduces the number of addresses that can be allocated as public
Internet Protocol is a unique ID which distinguishes one computer from all the other in the world when connected
to the internet. The IP is a series of numbers which is called your IP address. IP was first standardized in September
1981. if a device wants to communicate using TCP/P, it needs an IP address. The specification required that each
system attached to an IP-based Internet be assigned a unique, 32-bit Internet address value.
Total Numbers For This
Class Of Network
220.127.116.11 to 18.104.22.168
2 – 2 (126)
Number Of Hosts Per
2 -2 (65,534)
2 – 2 (254)
CLASS A NETWORKS (/8 PREFIXES)
Each class A network address has an 8-bit network prefix, with the highest order bit set to 0 (zero) and a 7-bit
network number, followed by a 24-bit host number. Today, Class A networks are referred to as “/8s” (pronounced
“slash eight” or just “eights” ) since they have an 8-bit network prefix.
Au with the loopback range, the address range from 0.0.0.0 through 0.255.255.255 should not be considered part
of the normal Class A range. 0.x.x.x addresses serve no particular function in IP, but nodes attempting to use them
will be unable to communicate properly on the Internet.
IP LOOPBACK ADDRESS
127.0.0.1 is the loopback address in IP. Loopback is test mechanism of network adapters. Messages sent to
127.0.0.1 do not get delivered to the network. Instead, the adapter intercepts all loopback messages and returns
them to the sending application.
CLASS B NETWORKS (/16 PREFIXES)
Each class B network address has 16-bit network prefix, with the two highest order bits set to 1-0 and a 14-bit
network number, followed by a 16-bits host number. Class B networks are now referred to as “/16s” since they
have a 16-bit network prefix.
AUTOMATIC PRIVATE ADDRESS
An automatic Private IP Addressing (APIPA), feature that will automatically assign an Internet Protocol address to a
computer on which it installed. This occurs when the TCP/IP protocol is installed, set to obtain its IP address
automatically from a Dynamic Host Configuration Protocol server, and when there is no DHCP server present or
the DHCP server is not available.
CLASS C NETWORKS (/24 PREFIXES)
Each Class C network address has a 24-bit network prefix, with the three highest order bits set to 1-1-0 and a 21-bit
network number, followed by an 8bit host number. Class C networks are now referred to as “/24s” since they have
a 24-bit network prefix.
CLASS D AND MULTICAST
The IPv4 networking standard defines Class D addressed as reserved for multicast. Multicast is a mechanism for
defining groups of nodes and sending IP messages to that group rather than to every node on the LAN (broadcast)
or just one other node (unicast).
CLASS E AND LIMITED BROADCAST
The IPv4 networking standard defines Class E addressed as reserved, meaning that they should not be used on IP
networks. Some research organizations use Class E addressed for experimental purposes. However, nodes that try
to use these addresses on the internet will be unable to communicate properly. A special type of IP address is the
limited broadcast address 255.255.255.255.
A subnet allows the flow of network traffic between hosts to be segregated based on a network configuration. By
organizing hosts into logical groups, subnetting can improve network security and performance.
Perhaps the most recognizable aspect of subnetting is the subnet mask. Like IP addresses, a subnet mask contains
four bytes (32bits) and is often written using the same “dotted-decimal” notation.
APPLYING A SUBNET MASK
A subnet mask neither works like an IP address, nor does it exists independently from them. Instead, subnet masks
accompany an address and the two values work together. Applying the subnet mask to an IP address splits the
address into two parts, an “extended network address” and a host address.
For a subnet mask to be valid, its leftmost bits must be set to ‘1’. For example,
00000000 00000000 00000000 00000000
is an invalid subnet mask because the leftmost bit is set to ‘0’.
Conversely, the rightmost bits in a valid subnet mask must be set to ‘0’ not ‘1’. Therefore,
11111111 11111111 11111111 11111111
Public IP addresses are IP addresses that are visible to the public. Because these IP addresses are public, they allow
other people to know about and access your computer, like a Web server. In some cases, you do not want people
to access your computer or you want to restrict certain individuals from accessing your computer or server.
The IP standard defines specific address ranges within Class A, Class B and Class C reserved for use by private
networks (intranets). The table below lists these reserved ranges of the IP address space.
Private start address
Private finish address
Nodes are effectively free to use addresses in the private ranges I they are not connected to the Internet, or if they
reside behind firewalls or other gateways that use Networks Address Translation (NAT).
In computer networking, a broadcast address is an IP address that allowa information to be sent to all machines on
a given subnet rather than a specific machine. That exact notation can vary by operating system.
Generally, the broadcast address is found by taking the bit complement of the subnet mask and then OR-ing it
bitwise with the IP address.
Example: to broadcast a packet to an entire class B subnet using a private IP address space, the broadcast address
would be 172.16.255.255.
Classless Inter Domain Routing (CIDR)
Classless Inter Domain Routing. CISR was invented several years ago to kep the internet from running out of IP
addresses. CIDR was introduced to improve both address space utilization and routing scalability in the internet. It
was needed because of the rapid growth of the Internet and growth of the IP routing tables held in the Internet
routers The “classfull” system of allocating IP addresses can be very wasteful; anyone who could reasonably show
a need for more that 254 host addresses was given a Class B address Block of 65533 host addresses.
To convert an IP dotted-quad address to binary, take each decimal number of the dotted-quad and look up the
binary equivalent in the Binary Convrsion Table below. You will have a 32-bit binary numbers as the result.
Subnetting, as this process is more commonly called, is a remarkably logical and mathematical process.
Understanding the mathematics of subnetting helps you develop and implement efficient subnetting schemes that
make better use of available address spaces. That is the explicit goal of subnetting to use an address space more
A class A, B, or C TCP/IP network can be further divided, or subnetted, by a system administrator. This becomes
necessary as you reconcile the logical address scheme of the Internet (abstract world of IP addresses and subnets)
with the physical networks in use by the real world.
What are the valid hosts?
Valid hosts are the numbers between the subnets, omitting the all 0s and all 1s. For example, if 16 is the subnet
number and 31 is the broadcast address, then 17-30 is the valid host range – it’s always the numbers between the
subnet address and the broadcast address.
Fixed-length subnet mask (FLSM)
The first significant feature retrofitted to the IPv4 address space was the introduction of support for a third tier in
its architecture. “Classical IP: The Way It Was,” the IP address space features a two-tier hierarchy in which each
address consists of a network address and a host address within its 32-bit structure. Such flatness distinctly limits
scalability in a number of ways.
Step 1: Router R1 needs 20 network addresses. So,
2 = 32-2 (2 is subtract form 32 because in FLSM all 0’s and all 1’s are not consider) = 30
Step 2: Now borrow 5 bit from the host part of the IP address.
Step 3:So the subnet mask is change, now new subnet mask is
255.255. (128+64+32+26+8) 000.00000000
Step 4: After calculating subnet mask, the first network address is
Put 1 at the rightmost bit of the network part, like
IP is 22.214.171.124/21
(CIDR is 21 because 8 bit + 8 bit + 5 bit)
Step 5: Now the first host address of this network address is
172.16.8.00000001 = 172.16.8.1/21 (Fast host address)
172.16.8.00000010 = 172.16.8.2/21
172.16.8.00000011 = 172.16.8.3/21
172.16.8.11111110 = 172.16.8.254/21 (last host address)
Step 6: Second network calculation
Put 1 in the second bit if the network part like,
172.16.16.0 / 21
Step 7: Go to step 5 for host address calculation
Step 8: Do the same method for R2 router.
Variable – length subnet mask (VLSM)
A VLSM is a sequence of numbers of variable length that streamlines packet routing within the subnets of a
proprietary network. A subnet can be a geographically defined local area network (LAN). Alternatively a subnet
may define security boundaries, departmental boundaries, multicast or hardware security parameters.
In VLSM, considered the maximum number of host present in a network.
Here R2 router has maximum number of hosts.
So, requirements is 50 hosts
2 = 64
So, we have to leave 6 bit form the host part of the IP
So, the subnet mask is 8+8+8+2 = 26
Now network address for R2 is 126.96.36.199 / 26
Now calculate the 2 network address from 188.8.131.52 / 26
172.168.00000000.00000000 / 26
Put 1 at the last bit of network part.
172.168.00000000.01000000 / 26
So 2 network address is 184.108.40.206 / 26
Now we calculate the network address of R1 for 2 network address.
172.168.00000000.01000000 / 26
Requirement of R1 is 28 hosts.
2 = 32
So, network address for r1 is 220.127.116.11 / 27
Repeat step 3 for calculate 3 network address and step 4 for calculate network
address between two routers.
You will often come across Wildcard masks, particularly if you work with OSPF and / or Cisco routers. The use of
wildcard masks is most prevalent when building Access Control Lists (ACLs) on Cisco routers. ACLs are filters and
make use of wildcard masks to define the scope of the address filter. Although ACL wildcard masks are used with
other protocols, we will concentrate on IP here.
Routing is a process by which router consider the best path to the destined device amongst to the laded physical
circuit to reach the remote site. The election of the best path depends on various parameters and metrics, like
bandwidth, time delay, HOP count, congestion and many more. The whole result after the election of a best path
that is also known as route is captured or stored under the router memory in a form of Table, i.e. known as
If your network has no routers, then it should be apparent that you are not routing. Routers route traffic to all the
networks in your internet work. To be able to route packets, a route must know , at a minimum, the following:
Neighbour routers from which it can learn about remote networks
Possible routes to all remote network
How to maintain and verify routing information.
The router learns about remote networks from neighbour routers or from an administrator. The router then builds
a routing table (a map of the internetwork) that describes how to find the remote networks. If a network is directly
connected, then the router already knows how to get to it.
Routing protocols use metrics to evaluate what path will be the best for a packet to travel. A metric is a standard of
measurement, such as path bandwidth, that is used by routing algorithms to determine the optimal path to a
destination. To aid the process of path determination, routing algorithms initialize and maintain routing tables,
which contain route information. Route information varies depending on the routing algorithm used.
Routing algorithms fill routing tables with a variety of information. Destination/next hop association tell a router
that a particular destination can be reached optimally by sending the packet to a particular router representing the
“next hop” on the way to the final destination.
Routing tables contain information used by switching software to select the best route. But how, specifically, are
routing tables built? What is the specific nature of the information that they contain? How do routing algorithms
determine that one route is preferable to others?
Routing algorithms have used many different metrics to determine the best route. Sophisticated routing
algorithms can base route selection on multiple metrics, combining them in a single (hybrid) metric. All the
following metrics have been used:
Path length is the most common routing metric. Some routing protocols allow network administrators to assign
arbitrary costs to each network link. In this case, path length is the sum of the costs associated with each link
Reliability in the context of routing algorithms, refers to dependability (usually described in terms of the bit-error
rate) of each network link. Some network links might go down more often than others. After a network fails,
certain network links might be repaired more easily or more quickly than other links.
Delay , Routing delay refers to the length of time required to move a packet from source to destination through
the internetwork. Delay depends on many factors, including the bandwidth of intermediate network links, the port
queues at each router along the way, network congestion on all intermediate network links, the physical distance
to be traveled.
Bandwidth refers to the available traffic capacity of a link; all other things being equal, a 10Mbps Ethernet link
would be preferable to a 64-kbps leased line. Although bandwidth is a rating of the maximum attainable
throughput on a link, routes through links with greater bandwidth do not necessarily provide better routes than
routes through slower links.
Load refers to the degree to which a network resource, such as a router, is busy. Load can be calculated in a variety
of ways, including CPU utilization and packets processed per second. Monitoring these parameters on a continual
basis can be resource-intensive itself.
Communication cost another important metric, especially because some companies may not care about
performance as much as they care about operating expenditures.
Configuring IP routing
Once you create an internetwork by connect LANs and WANs to a router, you will need to configure the router
with the IP addresses. And after that to route the data packets you have to configure IP routing properly using 1 of
For the router R1 we have to configure total 4 interfaces with IP address along with the host name for each router
to identify easily. When we start configuring a router with IP address and host name why not configure the banner
and password for the same? It better to adapt the habit to configure a full, it will help you alter on.
Now we are ready to configure the next router that is R2. we have to configure router R2 in the same way as we
configured Router R1, only difference is, in router R2 we will not give the same IP addresses as well as the same
Hostname and password along with Banner and description.
Static Routing is not really a protocol, simply the process of manually entering routes into the routing table via a
configuration file that is loaded when the routig device starts up. As an alternative, these routes can be entered by
a network administrator who configures the routes. Since these routes don’t change after they are configured
(unless a human changes them) they are called ‘static’ routes.
Static Routing has the following Benefits:
You can use cheaper router due to less processor overhead than that of dynamic routing, where the
processor’s overhead is maximum. The processor overhead is less because all the routes are configured
manually by the network administrator, so router need not bother about finding or establishing route.
The cost for ISP link is saved, because in case of static routing, router doesn’t take unnecessary WAN link
bandwidth for route convergence (convergence means, upgrading, finding or establishing a route in the
Routing Table of a router.).
It adds security because the administrator can choose to allow routing access to certain networks only.
Static Routing has the following Demerits
The administrator have some sound knowledge about the network topology to configure a router for
static routing, because administrator is only liable to give the route information to the router to deliver
data packets from or to a Network.
At the time of Network expansion, the new network’s information or route should provided to the entire
router’s routing table by hand by administrator.
It’s not a handy for the large network, because maintaining would be a full-time job in time.
DESTINATION NETWORK ADDRESS:
The network which the administrator wants to place into the routing table.
The subnet masks which is used by the destination network.
The address of the next HOP router that will receive the packet and forward the same to the destine network. This
is a router interface that’s on a directly connected network. Before going to configure the static route check the
next HOP using the PING command and the PING utility must successes. If you configure wrong HOP address or the
router interface to that router is down, the static route will show UP in the router’s configuration but not in the
It is used in place of the next-hop address if you want, and shows up a directly connected route.
It is a number which represents the weight of a routing process or you may say that the priority of routing
algorithm. Like Static Route has the AD of 1 and directly connected route has AD0 by default. According to the AD
the router will judge which routing methods is to be use to determine and creating the routing table.
If the interface is logically down or the Next HOP router can’t be communicated by the source router, then the
entry for the route automatically will be discarded. To preserve the route at any circumstances we can use the
A default route, also known as the gateway of last resort, is the network route used by a outer when no other
known route exists for a given IP packet’s destination address. All the packets for destinations not known by the
router’s routing table are sent to the default route. This route generally leads to another router, which treats the
packet the same way. If the route is known, the packet will get forwarded to the known route. If not, the packet is
forwarded to the default-route of that router which generally leads to another router. And so on. Each router
traversal adds a one-hop distance to the route.
The default route in IPv4 (in CIDR notation) is 0.0.0.0 / 0, often clled the quad-zero routes. Since the subnet mask
given is /0, it effectively specifies no network, and is the “shortest” match possible. A route lookup that doesn’t
match anything will naturally fall back onto this route. Similarly, in IPv6 the default address is given by ::/0.
Dynamic routing protocols are software applications that dynamically discover network destinations and how to
get to them. A router will ‘learn’ routes to all directly connected networks first. It will then learn routes from other
routers that run the same routing protocol. The router will then sort through its list of routes and select one or
more ‘best’ routes for each network destination it knows or has learned.
A routing protocol is used by a router to dynamically find al, the networks in the internetwork and to ensure that
the all the routers have the same routing table. Basically a routing protocol determines the path of a packet
through an internetwork. Examples of routing protocols are IGRP, BGP, RIP, OSPF etc.
When all routers know about the internetwork paths a routed protocol can be used to send user data packets
through the established path. Routed protocols are assigned to an interface and determine the method of packet
delivery. Examples of routed protocols are IPv4 and IPv6 and IPX etc.
ROUTING PROTOCOL BASICS:
Before looking deeper into RIP, there are several important things that you need to know about routing protocols.
You need to have an in-depth knowledge about administrative distances, the three different kinds of routing
protocols and finally routing loops. We will look at each of these in details in the following chapters.
The administrative distance is used to judge the level of reliability of converged routing information election the
best route to a neighbouring or remote router. An administrative distance is represented by numeric from 0 to
255, where the 0 is the most trusted and 255 means no traffic can pass through it. If a router receives two updates
listing the same remote network, the first thing the router checks it the AD. If one of advertise route contained
with lower AD than other, the route with lower AD will placed in the routing table.
The routing protocols can be divided in to three subsequent groups, they are described.
The distance is the main parameter for the distance vector routing protocols, means the best path for the remote
network is only be judging by the Distance. Each time when a packet passes through a router is called a HOP, and
this HOP is counted as the metric for the best route election or selection.
In link state protocols, also called shortest-path-first protocols, each router creates three separate tables. One of
these table get track of directly attached neighbour information, one determines the physical orientation
(topology) of the entire internetwork, and the last one is used as the Routing Table.
Hybrid protocols used both aspects of Link-state as well as Distance Vector algorithm. EIGRP is an example of
Hybrid routing protocol.
Data Terminal Equipment: any device located at the user end of a user-network interface serving as destination, a
source or both. DTE includes devices such as multiplexers, routers, protocols translators and computers. The
connection to a data network is made through data communication equipment (DCE) such as a modem, using the
clocking signals generated by that device.
Data Communication Equipment ( as defined by the EIA) or data circuit-terminating equipment (as defined by the
ITU-T): The mechanism and links of a communications network that make up the network portion of the user-tonetwork interface, such a modems. The DCE supplies the physical connection to the network, forwards traffic, and
provides a clocking signal to synchronize data transmission between DTE and DCE devices.
ROUTING INFORMATON PROTOCOL:
The routing information protocol, or RIP, as it is more commonly called, is one of the most enduring of all routing
protocols. RIP is also one of the more easily confused protocols because a variety of RIP-like routing protocols
proliferated, some of which even used the same name! RIP and the myriad RIP-like protocols based on the set of
algorithms that use distance vectors to mathematically compare routes to identify the best path to any given
RIP sends routing-update message at regular intervals and when the network topology changes. When a router
receives a routing update that includes changes to an entry, it updates its routing table to reflect the new route.
RIP ROUTING METRIC:
RIP uses a single routing metric (hop count) to measure the distance between the siurce and a destination
network, each hop in a path from source to destination is assigned a hop count value, which is typically 1.
RIP uses numerous timers to regulate it performance. These include a routing – update timer, a route time out
timer, and a route-flush timer. The routing-update timer clocks the interval between periodic routing updates.
ROUTE UPDATE TIMER:
Sets the interval (typically 30 seconds) between periodic routing updates in which the router sends a complete
copy of its routing table out to all neighbours.
ROUTE INVALID TIMER:
Determines the length of time that must elapse (180 seconds) before a router determines that a route has become
invalid. It will come to this conclusion if it hasn’t heard any updates about a particular route for that period.
This sets the amount of time during which routing information is suppressed. Routes will enter into the holddown
state when an update packet is received that indicated the route is unreachable. The default is 180 seconds.
ROUTE FLUSH TIMER:
Sets the time between a route becoming invalid and its removal from the routing table (240 seconds). Before its
removal from the table, the router notifies its neighbours of the route’s impending demise. The value of the route
invalid timer must be less than that of the route flush timer.
CONFIGURING RIP ROUTIING:
To configure RIP routing, just turn on the protocol with the ROUTER RIP command and tell the RIP routing protocol
which networks to advertise. That’s it. Let’s configure our three router internertwork (Scenario 3) with RIP routing.
1. Distance Vector
1. Distance Vector
2. Maximum hop count 15
2. Maximum hop count 15
4. Broadcast based
4. Uses multicast 18.104.22.168
5. Do not support VLSM
5. Supports VLSM networks
6. No authentication
6. Allows for MD5 authentication
7. No support for discontiguous networks.
7. Supports discontiguous networks.
MAXIMUM HOP COUNT:
The routing loop problem can continue to the infinity, the main cause of this due to broadcasts the entire routing
table to all active interfaces and wrong information being communicated and propagated throughout the
internetwork. Without some form of intervention, the hop count increases indefinitely each time a packet passes
through a router.
Split horizon is another solution to stop the routing kloop. This mechanism reduces erroneous routing information
and routing overhead in a distance-vector network by enforcing the rule that routing information cannot be sent
back in the direction from which it was received.
Another way to stop routing loops caused by fickle updates is route poisoning. For example, when NetC goes
down, R5 initiates route poisoning by advertising NetC as 16, or reachable (sometimesreferred to as infinite).
This poisoning of the route to NetC keeps R3 from being susceptible to incorrect updates about the route to NetC.
A holddown is prevented by regular update messages from reinstating a route that is going up and down. This is
called flapping. When a serial link is losing connectivity and then coming back up this happens. The entire network
could be brought down by that one flapping interference if there was no way to stabilize this.
While the initial configuration of your Cisco router using the console port and a rollover cable may be necessary,
you will eventually want to access routers on your network using telnet sessions. Since telnet is an IP-based
application, your routers will need to be configured with atleast one valid and reachable IP address to use this
method. Also remember that in order to connect to a router using telnet, that router will need a virtual terminal
(vty) password configured.
[Connection to accra closed by foreign host]
CISCO DISCOVERY PROTOCOL (CDP):
The Cisco Discovery Protocol (CDP) is a proprietary layer 2 network protocol developed by Cisco Systems which
runs on most Cisco equipment and is used to share information about other directly connected Cisco equipment
such as the operating system version and IP address. CDO can also be used for On Demand Routing (ODR) which is
a method of including routing information in CDP announcements so that dynamic routing protocols do not need
to be used in simple networks.
Cisco Discovery Protocol CDP) is primarily used to obtain protocol address of neighbouring devices and discover
the platform of those devices. CDP can also be used to show information about the interfaces your router uses.
CDP runs on all media that supports Subnetwork Access Protocol (SNAP), including local-area network (LAN),
Frame Relay, and Asynchronous Transfer Mode (ATM) physical media. CDP runs over the data link layer only.
CDP DEFAULT CONFIGURATION
CDP global enable state
CDP pot enable state
Enabled on all ports
CDP message interval
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
Setting the Holdtime and Timer
Use the following commands to set CDP timer and holdtime values.
Enter configuration commands, one per line. End with CNTL/Z
Router_2 (config) #cdp timer 90
Router_2 (config) #cdpholdtime 360
SHOW CDP ENTRY
The show cdp entry [device id] command shows more information about the specified neighbour.
Router_2#show cdp entry Router1
Modes in routers
1. User Mode or Console Mode
2. Priveledge mode or enable mode
3. Global configuration
sign of mode
Command to go at priviledge mode
Command to go at Global configuration mode
Command to go to previous mode
User mode :- It allow an administrator to perform very few commands. One can only
verify statistics in user mode. One cannot see or change the router configuration.
Priviledge mode:- It enables user to view and change the configuration.
Global configuration :- It allows user to change those router configuration that effects
the entire router.
Basic commands in Routers
Giving ip address on Serial port
Config# int s0/0
Config# ip address 10.0.0.1 255.0.0.0
Clock rate 64000
Giving ip address on Fast Ethernet port
Config# int f0/0
Config# ip address 22.214.171.124 255.255.255.0
Config# banner motd #
Changing hostname of router
Config# Host name newhostname
Setting enable password
Config#enable password talvinder
Setting enable(secret) password
Config#enable secret talvinder
Config# No enable password
Config# No enable secret
Setting console password
Config# line console 0
# Show running_config
How to see the Ipaddress(individually)
#show int s0/0 (serial port)
#show int f0/0 (Ethernet)
How to see ip address in brief manner
#show ipint brief
How to see protocols
How to clear counters
#clear counters s0/0
Internal configuration components
RAM – contains dynamic/ running configuration
NVRAM-Contains back up of configuration(start uo configuration)
Flash- Contains copy of cisco IOS
ROM- contains subset of IOS, bootable IOS image.
Router startup sequence
1.Bootstrap program loaded from ROM
2.Bootstrap runs the POST
3.Bootstrap locates IOS in flash.
4.IOS is expanded and then loaded into RAM
5.once IOS is loaded into RAM, it looks for startup config in NVRAM.
6.If found the configuration is loaded into RAM.