Learn basics of ip addressing

Learn Basics of IP addressing
Presented by
Bobby Agustinus Ginting
Microwave/IPRAN Manager

Agenda:
 Layers
 OSI and TCP/IP Layers
 TCP/IP Technology
 What is IP?
 IPv4 Structure
 Binary Basics
 IP Classes
 Subnetting
 TOOLS

Layers
Complex problems can be solved using the common divide and conquer principle. In this case the internals of the
Internet are divided into separate layers.
Makes it easier to understand Developments in one layer need not require changes in another layer
Easy formation (and quick testing of conformation to) standards
The OSI Model (Open Systems Interconnection Model) is a conceptual framework used to describe the functions of a
networking system. The OSI model characterizes computing functions into a universal set of rules and requirements in
order to support interoperability between different products and software. In the OSI reference model, the communications
between a computing system are split into seven different abstraction layers: Physical, Data Link, Network, Transport,
Session, Presentation, and Application.
Created at a time when network computing was in its infancy, the OSI was published in 1984 by the International
Organization for Standardization (ISO). Though it does not always map directly to specific systems, the OSI Model is
still used today as a means to describe Network Architecture.
ISO is the organization.
OSI is the model.

the concept of layers in our daily life
Layers

Two main models of layers are used:
 OSI (Open Systems Interconnection)
 TCP/IP
OSI and TCP IP Layers

The 7 Layers of the OSI Model
Layer 7 Application
(Software App Layer-Directory Services, email, network management, file transfer, web page , database access)
Layer 6 Presentation
(Syntax/semantics Layer, Data translation, compression, encryption/decryption, formatting)
Layer 5 Session
(Application Session Management-Session establishment/teardown, file transfer checkpoints, interactive login)
Layer 4 Transport
(End to end Transportation Service-Data segmentation, reliability, multiplexing, connection-oriented, flow
control, sequencing, error checking)
Layer 3 Network
(Routing-packets, subnetting , logical IP Addressing , path determination, connectionless)
Layer 2 Data link
(Switching – Frame traffic control, CRC error checking , encapsulates packets, MAC addresses)
Layer 1 Physical
(Cabling/Network Interface-Manages physical connection, interpretation of bit stream into electrical signal)
Acronym: All People Seem To Need Data Processing

Layer 1 - Physical Layer
The lowest layer of the OSI Model is concerned with electrically or optically transmitting raw unstructured data
bits across the network from the physical layer of the sending device to the physical layer of the receiving device.
It can include specifications such as voltages, pin layout, cabling, and radio frequencies. At the physical layer,
one might find “physical” resources such as network hubs, cabling, repeaters, network adapters or modems.
The physical layer is responsible for movements of
individual bits from one hop (node) to the next.
Services
• Bit-by-bit or symbol-by-
symbol delivery
• Modulation
• Line coding
• Bit synchronization
• Start-stop signalling
• Circuit switching
• Multiplexing
• Carrier sense and collision
detection
• Physical network topology,
like bus, ring, mesh or star
network
• ...

Layer 2 - Data Link Layer
At the data link layer, directly connected nodes are used to perform node-to-node data transfer where data is
packaged into frames. The data link layer also corrects errors that may have occurred at the physical layer.
The data link layer encompasses two sub-layers of its own. The first, media access control (MAC), provides flow
control and multiplexing for device transmissions over a network. The second, the logical link control (LLC),
provides flow and error control over the physical medium as well as identifies line protocols.
The data link layer is responsible for moving
frames from one hop (node) to the next.

Hop-to-hop delivery
Services
• Encapsulation
• Frame synchronization
• Logical link control (Error & Flow
control)
• Media access control (MAC, LAN
switching, Physical addressing, QaS,
VLAN, ...)

Layer 3 - Network Layer
The network layer is responsible for receiving frames from the data link layer, and delivering them to their intended
destinations among based on the addresses contained inside the frame. The network layer finds the destination by
using logical addresses, such as IP (internet protocol). At this layer, routers are a crucial component used to quite
literally route information where it needs to go between networks.
The network layer is responsible for the delivery of individual packets from
the source host to the destination host.

Source-to-destination delivery
Functions
• Connection model
• Host addressing
• Message forwarding

Layer 4 - Transport Layer
The transport layer manages the delivery and error checking of data packets. It regulates the size, sequencing, and
ultimately the transfer of data between systems and hosts. One of the most common examples of the transport
layer is TCP or the Transmission Control Protocol.
The transport layer is responsible for the delivery
of a message from one process to another.

Reliable process-to-process delivery of a message
Services
• Connection-oriented
communication
• Same order delivery
• Reliability
• Flow control
• Congestion avoidance
• Port Multiplexing

Layer 5 - Session Layer
The session layer controls the conversations between different computers. A session or connection
between machines is set up, managed, and termined at layer 5. Session layer services also include
authentication and reconnections.
Services
• Authentication
• Authorization
• Session restoration
The session layer is responsible for dialog
control and synchronization.

Layer 6 - Presentation Layer
The presentation layer formats or translates data for the application layer based on the syntax or semantics that the
application accepts. Because of this, it at times also called the syntax layer. This layer can also handle the encryption
and decryption required by the application layer.
The presentation layer is responsible for translation, compression, and
encryption.

Services
• Data conversion
• Character code translation
• Compression
• Encryption and Decryption

Layer 7 - Application Layer
At this layer, both the end user and the application layer interact directly with the software application. This
layer sees network services provided to end-user applications such as a web browser or Office 365. The
application layer identifies communication partners, resource availability, and synchronizes communication.
The application layer is responsible for
providing services to the user.

Summary of layers

Introduction
In the two decades since their invention, the heterogeneity of networks has expanded further with the
deployment of Ethernet, Token Ring, Fiber Distributed Data Interface (FDDI), X.25, Frame Relay,
Switched Multimegabit Data Service (SMDS), Integrated Services Digital Network (ISDN), and most
recently, Asynchronous Transfer Mode (ATM). The Internet protocols are the best proven approach to
internetworking this diverse range of LAN and WAN technologies.
The Internet Protocol suite includes not only lower-level specifications, such as Transmission Control
Protocol (TCP) and Internet Protocol (IP), but specifications for such common applications as electronic
mail, terminal emulation, and file transfer. Figure 1 shows the TCP/IP protocol suite in relation to the
OSI Reference model. Figure 2 shows some of the important Internet protocols and their relationship
to the OSI Reference Model. For information on the OSI Reference model and the role of each layer,
please refer to the document Internetworking Basics.
The Internet protocols are the most widely implemented multivendor protocol suite in use today.
Support for at least part of the Internet Protocol suite is available from virtually every computer vendor.
TCP/IP Technology

Figure 1
TCP/IP Protocol Suite in Relation to the
OSI Reference Model
Figure 2
Important Internet Protocols in Relation to the OSI
Reference Model
TCP/IP Technology

TCP/IP Technology
TCP/IP Technology
This section describes technical aspects of TCP, IP, related protocols, and the environments in which
these protocols operate. Because the primary focus of this document is routing (a layer 3 function),
the discussion of TCP (a layer 4 protocol) will be relatively brief.
TCP
TCP is a connection−oriented transport protocol that sends data as an unstructured stream of
bytes. By using sequence numbers and acknowledgment messages, TCP can provide a sending
node with delivery information about packets transmitted to a destination node. Where data has
been lost in transit from source to destination, TCP can retransmit the data until either a timeout
condition is reached or until successful delivery has been achieved. TCP can also recognize
duplicate messages and will discard them appropriately. If the sending computer is transmitting
too fast for the receiving computer, TCP can employ flow control mechanisms to slow data
transfer. TCP can also communicates delivery information to the upper−layer protocols and
applications it supports. All these characteristics makes TCP an end−to−end reliable transport
protocol. TCP is specified in RFC 793 .

TCP/IP Protocol Suite in Relation to the OSI Reference Model

Packet Encapsulation
 The data is sent down the protocol stack
 Each layer adds to the data by prepending headers
22Bytes 20Bytes 20Bytes 4Bytes
64 to 1500 Bytes

TCP/IP suite of protocols
The TCP/IP suite is a set of protocols used on computer networks today (most notably on the Internet). It provides an end-to-end
connectivity by specifying how data should be packetized, addressed, transmitted, routed and received on a TCP/IP network.
This functionality is organized into four abstraction layers and each protocol in the suite resides in a particular layer.
The TCP/IP suite is named after its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol
(IP).
The following table shows which protocols reside on which layer of the TCP/IP model:

Wireshark Capture

TCP explained
One of the main protocols in the TCP/IP suite is Transmission Control Protocol (TCP). TCP provides reliable and
ordered delivery of data between applications running on hosts on a TCP/IP network. Because of its reliable
nature, TCP is used by applications that require high reliability, such as FTP, SSH, SMTP, HTTP, etc.
TCP is connection-oriented, which means that, before data is sent, a connection between two hosts must be
established. The process used to establish a TCP connection is known as the three-way handshake. After the
connection has been established, the data transfer phase begins. After the data is transmitted, the connection is
terminated.
One other notable characteristic of TCP is its reliable delivery. TCP uses sequence numbers to identify the order
of the bytes sent from each computer so that the data can be reconstructed in order. If any data is lost during the
transmission, the sender can retransmit the data.

Because of all of its characteristics, TCP is considered to be complicated and costly in terms of
network usage. The TCP header is up to 24 bytes long and consists of the following fields:
• source port – the port number of the application on the host sending the data.
• destination port – the port number of the application on the host receiving the data.
• sequence number – used to identify each byte of data.
• acknowledgment number – the next sequence number that the receiver is expecting.
• header length – the size of the TCP header.
• reserved – always set to 0.
• flags – used to set up and terminate a session.
• window – the window size the sender is willing to accept.
• checksum – used for error-checking of the header and data.
• urgent – indicates the offset from the current sequence number, where the segment of non-urgent data begins.
• options – various TCP options, such as Maximum Segment Size (MSS) or Window Scaling.
NOTE
TCP is a Transport layer protocol (Layer 4 of the OSI model).
TCP explained

UDP explained
One other important protocol in the TCP/IP site is User Datagram Protocol (UDP). This protocol is basically a scaled-
down version of TCP. Just like TCP, this protocol provides delivery of data between applications running on hosts on a
TCP/IP network, but, unlike TCP, it does not sequence the data and does not care about the order in which the segments
arrive at the destination. Because of this it is considered to be an unreliable protocol. UDP is also considered to be a
connectionless protocol, since no virtual circuit is established between two endpoints before the data transfer takes place.
Because it does not provide many features that TCP does, UDP uses much less network resources than TCP. UDP is
commonly used with two types of applications:
• applications that are tolerant of the lost data – VoIP (Voice over IP) uses UDP because if a voice packet is lost, by
the time the packet would be retransmitted, too much delay would have occurred, and the voice would be unintelligible.
• applications that have some application mechanism to recover lost data – Network File System (NFS) performs
recovery with application layer code, so UDP is used as a transport-layer protocol.
The UDP header is 8 bytes long and consists of the following fields:
Here is a description of each field:
source port – the port number of the application on the host sending the data.
destination port – the port number of the application on the host receiving the data.
length – the length of the UDP header and data.
checksum – checksum of both the UDP header and UDP data fields.
NOTE
UDP is a Transport layer protocol (Layer 4 of the OSI model).

Protocol

Ports explained
A port is a 16-bit number used to identify specific applications and services. TCP and UDP specify the source and
destination port numbers in their packet headers and that information, along with the source and destination IP addresses
and the transport protocol (TCP or UDP), enables applications running on hosts on a TCP/IP network to communicate.
Applications that provide a service (such as FTP and HTTP servers) open a port on the local computer and listen for
connection requests. A client can request the service by pointing the request to the application’s IP address and port. A
client can use any locally unused port number for communication. Consider the following example:
In the picture above you can see that a host with an IP address of
192.168.0.50 wants to communicate with the FTP server. Because FTP
servers use, by default, the well-known port 21, the host generates the
request and sends it to the FTP server’s IP address and port. The host use
the locally unused port of 1200 for communication. The FTP server receives
the request, generates the response and sends it to the host’s IP address and
port.
NOTE
The combination of an IP address and a port number is called a socket. In our
example the socket would be 192.168.0.50:1200.

Port numbers are from 0 to 65535. The first 1024 ports are reserved for use by certain privileged services:
Ports explained

What is IP?
An IP stands for internet protocol. An IP address is assigned
to each device connected to a network. Each device uses an
IP address for communication. It also behaves as an identifier
as this address is used to identify the device on a network. It
defines the technical format of the packets. Mainly, both the
networks, i.e., IP and TCP, are combined together, so
together, they are referred to as a TCP/IP. It creates a virtual
connection between the source and the destination.
We can also define an IP address as a numeric address
assigned to each device on a network. An IP address is
assigned to each device so that the device on a network can
be identified uniquely. To facilitate the routing of packets,
TCP/IP protocol uses a 32-bit logical address known as
IPv4(Internet Protocol version 4).

An IP address consists of two parts, i.e., the first one is a network address, and the other one is a host
address.
There are two types of IP addresses: • IPv4
• IPv6
• IPv4 addresses
What is IPv4?
IPv4 is a version 4 of IP. It is a current version and the most commonly
used IP address. It is a 32-bit address written in four numbers separated
by 'dot', i.e., periods. This address is unique for each device.
For example, 172.16.254.1
What is IP?
Decomposition of an IPv4 address
from dot-decimal notation to its
binary value
The above example represents the IP address in which each group of numbers separated by periods is called an
Octet. Each number in an octet is in the range from 0-255. This address can produce 4,294,967,296 possible
unique addresses.

An IP address is divided into two parts. The first part designates the network address while the second part
designates the host address.
The IP address space is divided into different network classes. Class A networks are intended mainly for
use with a few very large networks, because they provide only 8 bits for the network address field. Class B
networks allocate 16 bits, and Class C networks allocate 24 bits for the network address field. Class C
networks only provide 8 bits for the host field, however, so the number of hosts per network may be a
limiting factor. In all three cases, the left most bit(s) indicate the network class. IP addresses are written in
dotted decimal format; for example, 34.0.0.1. Figure 3 shows the address formats for Class A, B, and C IP
networks.
What is IP?
Figure 3
Address Formats for Class A,
B, and C IP Networks

IP networks also can be divided into smaller units called subnetworks or "subnets." Subnets provide extra
flexibility for the network administrator. For example, assume that a network has been assigned a Class A
address and all the nodes on the network use a Class A address. Further assume that the dotted decimal
representation of this network's address is 34.0.0.0. (All zeros in the host field of an address specify the
entire network.) The administrator can subdivide the network using subnetting. This is done by "borrowing"
bits from the host portion of the address and using them as a subnet field, as depicted in Figure 4.
Figure 4 Borrowing" Bits
What is IP?
 Responsible for end to end transmission
 Sends data in individual packets
 Maximum size of packet is determined by the networks
 Fragmented if too large
 Unreliable
 Packets might be lost, corrupted, duplicated, delivered out of order

The number of bits that can be borrowed for the subnet
address varies. To specify how many bits are used to
represent the network and the subnet portion of the
address, IP provides subnet masks. Subnet masks use
the same format and representation technique as IP
addresses. Subnet masks have ones in all bits except
those that specify the host field.
For example, the subnet mask that specifies 8 bits of
subnetting for Class A address 34.0.0.0 is 255.255.0.0.
The subnet mask that specifies 16 bits of subnetting for
Class A address 34.0.0.0 is 255.255.255.0. Both of these
subnet masks are pictured in Figure 5. Subnet masks
can be passed through a network on demand so that
new nodes can learn how many bits of subnetting are
being used on their network.
If the network administrator has chosen to use 8 bits of subnetting, the second octet of a Class A IP
address provides the subnet number. In our example, address 34.1.0.0 refers to network 34, subnet 1;
address 34.2.0.0 refers to network 34, subnet 2, and so on.
Figure 5 Subnet Masks
What is IP?

However, because of the growth of the Internet and the depletion of available IPv4 addresses, a new
version of IP (IPv6), using 128 bits for the IP address, was standardized in 1998. IPv6 deployment has
been ongoing since the mid-2000s.
• IPv6 addresses
In IPv6, the address size was increased from 32 bits in IPv4 to 128 bits, thus providing up to 2128 (approximately
3.403×1038) addresses. This is deemed sufficient for the foreseeable future.
The intent of the new design was not to provide just a sufficient quantity of addresses, but also redesign routing in
the Internet by allowing more efficient aggregation of subnetwork routing prefixes. This resulted in slower growth of
routing tables in routers. The smallest possible individual allocation is a subnet for 264 hosts, which is the square of
the size of the entire IPv4 Internet. At these levels, actual address utilization ratios will be small on any IPv6 network
segment. The new design also provides the opportunity to separate the addressing infrastructure of a network
segment, i.e. the local administration of the segment's available space, from the addressing prefix used to route
traffic to and from external networks. IPv6 has facilities that automatically change the routing prefix of entire
networks, should the global connectivity or the routing policy change, without requiring internal redesign or manual
renumbering.
What is IP?

The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and,
where appropriate, to be aggregated for efficient routing. With a large address space, there is no need
to have complex address conservation methods as used in CIDR.
All modern desktop and enterprise server operating systems include native support for IPv6, but it is not
yet widely deployed in other devices, such as residential networking routers, voice over IP (VoIP) and
multimedia equipment, and some networking hardware.
Decomposition of an IPv6 address from hexadecimal representation to its binary value
What is IP?

IP Address structure
• Expressed as four decimal
• Each decimal is digitally represented by one byte. Gives that an address consists of 32 bit
(IPv4).
• Every host in DCN (Data Communication Network) is assigned an IP Addresss
• IP addresses are written in dotted decimal format
• Four sections are separated by dots
• Each section contains a number between 0 and 255
• Five Classes
A series of consecutive addresses assigned to each class
o Class A, B, and C; different network size
o Class D: multicast
o Class E: experiment
Two type of addresses:
 Public: “on Internet”
 Private : free use in isolated networks
Class A,B,C have public and private adresses

1 1 0 0 0 0 0 0 1 0 1 0 1 0 0 0 1 0 0 0 0 0 0 0 0 1 1 0 0 1 0 0
128
64
32
16
8
4
2
1
128
64
32
16
8
4
2
1
128
64
32
16
8
4
2
1
128
64
32
16
8
4
2
1
192.168.128.100
Bit Value :
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
255.255.255.255
8 bits
32 bits (4 bytes)
8 bits 8 bits 8 bits
Each 8 digit group represents number between 0 and 255
• 32/4==8
• 28
=256 (A power of two is a number of the form 2n where n is an
integer, that is, the result of exponentiation with number two as the
base and integer n as the exponent)
• But, computers number starting at 0, so to make a space of 256
numbers, we number from 0 to 255

Net/ Sub Net
Net/ Sub Net
Net/ Sub Net
Net/ Sub Net Net/ Sub Net
IP DCN
IP DATA COMMUNICATION NETWORK
• Every IP based DCN is divided into a number of Networks (“Nets”) which can be sub-divided into Sub-Networks (“Sub-Nets”).
• The Nets/Sub-Nets organize the addressing structure of DCN.
• Each Net/Sub-Net is assigned a certain address range.
• Interconnection of Nets/Sub-nets is performed by Routers.

Each IP Address has two fundamentals parts:
• The network portion, which describes the physical wire
the device is attached to.
• The host portion, which identifies the host on that wire
• How can we tell the difference between the two sections?
• The network mask shows us where to split the network
and host section.
• Each place there is a 1 in the network mask, that binary
digit belongs to the network portion of the address.
• Each place there is a 0 in the network mask, that binary
digit belongs to the host portion of the address.
10.1.1.1
00001010 00000001 00000001 00000001
Host
Network
11111111 11111111 11111111 00000000
255.255.255.0

An alternative set of terminology is:
• The network portion of the address is called the
prefix.
• The host portion of the address is called the host.
• The network mask is expressed as a prefix length,
which is a count of the number of 1’s in the subnet
mask.
00001010 00000001 00000001 00000001
Host
Prefix
11111111 11111111 11111111 00000000
8 + 8 + 8 = 24
10.1.1.1

• The network address is the IP address with all 0’s in
the host bits.
• The broadcast address is the IP address with all 1’s
in the host bits.
• Packets sent to either address will be delivered to
all the hosts connected to the wire.
10 1 1 0/24
prefix host
00001010 000000011 00000001 00000000
these bits are 0, so this is the network address

What is Binary?
• Binary is nothing more than a System of Counting
• Everything in a computer’s brain comes down 0’s & 1’s
• Binary existed before computers
• Binary is an ON or OFF counting system, all or nothing. ‘1’ represents ON, ‘0’ represents OFF.
• Because each digit in binary can have 2 values, the base is 2 (see the example below for clarification)
1. Below is an 8 digit binary number
2. We calculate binary from right to left
3. Because it’s a base 2 system, each digit is 2 to the power of
(n). (n) refers to the placement of the number.
4. A binary number is pretty much telling us whether or not we
are using that value
Binary Basics

5. The 1 value tells us we are using that value (represented by green checkmarks) & the 0
value tell us we are not using that value (represented by red X’s).
6. The first digit in this example is representing that the value 2 to the power of 0 is ON
7. The second digit (2 to the power of 1) is OFF so the value is 0.
Binary Basics

Let’s calculate the rest of the values & add the ones that
are ON together…
What we just did can be represented in the following equation:
Binary Basics

How to Convert Decimal Numbers to Binary Numbers?
To convert decimal to binary numbers, proceed the steps given below:
1. Divide the given decimal number by “2” where it gives the result along with the remainder.
2. If the given decimal number is even, then the result will be whole and it gives the remainder “0”
3. If the given decimal number is odd, then the result is not divided properly and it gives the remainder “1”.
4. By placing all the remainders in order in such a way, the Least Significant Bit (LSB) at the top and Most
Significant Bit (MSB) at the bottom, the required binary number will obtain.
Now, let us convert the given decimal number 294 into a binary number.
Therefore, the binary equivalent for the given
decimal number 29410 is 1001001102
29410 =1001001102
Binary Basics

Decimal to Binary Conversion Example
A final larger example convert decimal 200 to binary code
200=128+64+8=27+ 26+ 23 =11001000
Once you are happy with the process then you can use a binary to decimal calculator like the one on
windows.
and this converts decimal numbers to binary
This converts binary numbers to decimal
Binary Basics

IP Classes
Classes of IP addresses
TCP/IP defines five classes of IP addresses: class A, B, C, D, and E. Each class has a range of valid
IP addresses. The value of the first octet determines the class. IP addresses from the first three
classes (A, B and C) can be used for host addresses. The other two classes are used for other
purposes – class D for multicast and class E for experimental purposes.
The system of IP address classes was developed for the purpose of Internet IP addresses
assignment. The classes created were based on the network size. For example, for the small number
of networks with a very large number of hosts, the Class A was created. The Class C was created for
numerous networks with small number of hosts.
Classes of IP addresses are:

Class A Public Address
Class A addresses are for networks with large number of total hosts. Class A allows for 126 networks by using the first
octet for the network ID. The first bit in this octet, is always set and fixed to zero. And next seven bits in the octet is all
set to one, which then complete network ID. The 24 bits in the remaining octets represent the hosts ID, allowing 126
networks and approximately 17 million hosts per network. Class A network number values begin at 1 and end at 127.
• Range: 1.0.0.0 to 126.0.0.0
• First octet value range from 1 to 127
• Subnet Mask: 255.0.0.0 (8 bits)
• Number of Networks: 126
• Number of Hosts per Network: 16,777,214
IP Classes

Class B Public Address
Class B addresses are for medium to large sized networks. Class B allows for 16,384 networks by using the first
two octets for the network ID. The two bits in the first octet are always set and fixed to 1 0. The remaining 6 bits,
together with the next octet, complete network ID. The 16 bits in the third and fourth octet represent host ID,
allowing for approximately 65,000 hosts per network. Class B network number values begin at 128 and end at 191.
• Range: 128.0.0.0 to 191.255.0.0
• Subnet Mask: 255.255.0.0 (16 bits)
• Number of Networks: 16,382
• Number of Hosts per Network: 65,534
IP Classes

Class C Public Address
Class C addresses are used in small local area networks (LANs). Class C allows for approximately 2 million
networks by using the first three octets for the network ID. In class C address three bits are always set and fixed
to 1 1 0. And in the first three octets 21 bits complete the total network ID. The 8 bits of the last octet represent
the host ID allowing for 254 hosts per one network. Class C network number values begin at 192 and end at 223.
• Range: 192.0.0.0 to 223.255.255.0
• Subnet Mask: 255.255.255.0 (24 bits)
• Number of Networks: 2,097,150
• Number of Hosts per Network: 254
IP Classes

Class D Address Class
Classes D are not allocated to hosts and are used for multicasting.
Range: 224.0.0.0 to 239.255.255.255
First octet value range from 224 to 239
Number of Networks: N/A
Number of Hosts per Network: Multicasting
IP Classes

Class E Address Class
Classes E are not allocated to hosts and are not available for general use. They are reserved for
research purposes.
• Range: 240.0.0.0 to 255.255.255.255
• Number of Networks: N/A
• Number of Hosts per Network: Research/Reserved/Experimental
IP Classes

Private Addresses
Within each network class, there are designated IP address that is reserved specifically for
private/internal use only. This IP address cannot be used on Internet-facing devices as that are
non-routable. For example, web servers and FTP servers must use non-private IP addresses.
However, within your own home or business network, private IP addresses are assigned to your
devices (such as workstations, printers, and file servers).
• Class A Private Range: 10.0.0.0 to 10.255.255.255
• Class B Private APIPA Range: 169.254.0.0 to 169.254.255.255
• Automatic Private IP Addressing (APIPA) is a feature on Microsoft Windows-
based computers to automatically assign itself an IP address within this range if
a Dynamic Host Configuration Protocol (DHCP) server is not available. A DHCP
server is a device on a network that is responsible for assigning IP address to
devices on the network.
• Class B Private Range: 172.16.0.0 to 172.31.255.255
• Class C Private Range: 192.168.0.0 to 192.168.255.255
Special Addresses
• IP Range: 127.0.0.1 to 127.255.255.255 are network testing addresses (also referred to as loop-back
addresses)
IP Classes

Subnet Masks and Gateways
A Subnet Mask defines which range of IP
Addresses are within a local network, and
which ones are not. Subnet masks always
work from left to right. Devices are said to
be within the same subnet if their IP
Address starts with the same digits, but
ends with a different set of digits.
Sometimes, it's easy to tell which part of an
IP address is part of the local network and
which is not (when the subnet mask
consists only sections that are 255 and 0),
but sometimes it may not be as clear.
Example IP Address 192.168.1.20
Subnet Mask 255.255.255.0
Starting Address in Subnet 192.168.1.0
Ending Address in Subnet 192.168.1.255
IP Classes

If the subnet mask is 255.255.255.0, then the first three octets of all devices must be the same. The
4th octet must be different and unique. A maximum of 254 devices can be used in this subnet.
If the subnet mask is 255.255.0.0, then the first two octets of all devices must be the same. The
combination of the last two octets must be different and unique. 65,534 devices can be used in this
subnet.
The very first address and very last address in a subnet are specially reserved addresses and
cannot be assigned to devices. Devices that are within the same subnet will be able to communicate
with one another, but a gateway is required to communicate with devices in different subnets. When
traffic is intended for a device outside of the subnet, it is sent to the gateway to be routed to the
correct destination. The gateway then sends the response back to the device that originally sent the
request and maintain a list of all IP addresses in use to avoid conflicts.
IP Classes

The IP address space is divided into different network classes.
Class A networks are intended mainly for use with a few very large networks, because they provide only
8 bits for the network address field.
Class B networks allocate 16 bits, and Class C networks allocate 24 bits for the network address field.
Class C networks only provide 8 bits for the host field, however, so the number of hosts per network may
be a limiting factor. In all three cases, the left most bit(s) indicate the network class. IP addresses are
written in dotted decimal format; for example, 34.0.0.1. In the figure below shows the address formats for
Class A, B, and C IP networks
IP Classes

Types of IP addresses
The IP addresses are divided into three different types, based on their operational characteristics:
1. unicast IP addresses – an address of a single interface. The IP addresses of this type are used for
one-to-one communication. Unicast IP addresses are used to direct packets to a specific host. Here is
an example:
In the picture above you can see that the host wants to communicate with the server. It uses the (unicast) IP
address of the server (192.168.0.150) to do so.

2. multicast IP addresses – used for one-to-many communication. Multicast messages are sent to IP multicast
group addresses. Routers forward copies of the packet out to every interface that has hosts subscribed to that group
address. Only the hosts that need to receive the message will process the packets. All other hosts on the LAN will
discard them. Here is an example:
R1 has sent a multicast packet destined for 224.0.0.9. This is an
RIPv2 packet, and only routers on the network should read it. R2
will receive the packet and read it. All other hosts on the LAN will
discard the packet.

3. broadcast IP addresses – used to send data to all possible destinations in the broadcast domain (the
one-to-everybody communication). The broadcast address for a network has all host bits on. For example,
for the network 192.168.30.0 255.255.255.0 the broadcast address would be 192.168.30.255*. Also, the IP
address of all 1’s (255.255.255.255) can be used for local broadcast. Here’s an example:
R1 wants to communicate with all hosts on the network and has
sent a broadcast packet to the broadcast IP address of
192.168.30.255. All hosts in the same broadcast domain will
receive and process the packet.
*This is because the subnet mask of 255.255.255.0 means that
the last octet in the IP address represents the host bits. And 8
one’s written in decimal is 255.

Subnetting
What Are Subnets Used for?
Subnets offer a way of organizing your network to help to reduce network congestion. When you
have a lot of traffic flowing between particular parts of your network, it can help to group those
parts in a single section, so the traffic doesn’t have to travel across the entire network to get from
place to place. Separating out small parts of your network into subnets allows traffic to flow more
quickly and to avoid taking unnecessary routes, adding traffic where it isn’t needed.
In addition, subnetting helps in efficiently allocating IP addresses and prevents large numbers of
IP addresses from going unused. Subnets are usually set up geographically for particular offices,
or for particular teams within a business to allow their network traffic to stay within the location.

Additional Information
If definitions are helpful to you, use these vocabulary terms in order to get you started:
• Address - The unique number ID assigned to one host or interface in a network.
• Subnet - A portion of a network that shares a particular subnet address.
• Subnet mask - A 32-bit combination used to describe which portion of an address refers to the subnet and which
part refers to the host.
• Interface - A network connection.
Subnetting

Subnetting
Subnetting is the practice of dividing a network into two or more smaller networks. It increases routing
efficiency, enhances the security of the network and reduces the size of the broadcast domain.
Consider the following example: In the picture above we have one huge network: 10.0.0.0/24. All
hosts on the network are in the same subnet, which has the
following disadvantages:
• a single broadcast domain – all hosts are in the same
broadcast domain. A broadcast sent by any device on the
network will be processed by all hosts, creating lots of
unnecessary traffic.
• network security – each device can reach any other device
on the network, which can present security problems. For
example, a server containing sensitive information shouldn’t
be in the same network as user’s workstations.
• organizational problems – in a large networks, different
departments are usually grouped into different subnets. For
example, you can group all devices from the Accounting
department in the same subnet and then give access to
sensitive financial data only to hosts from that subnet.

The network above could be subnetted like this:
Now, two subnets were created for different departments:
10.0.0.0/24 for Accounting and 10.1.0.0/24 for Marketing.
Devices in each subnet are now in a different broadcast
domain. This will reduce the amount of traffic flowing on the
network and allow us to implement packet filtering on the
router.
Subnetting

How to Calculate Subnets
Subnetting

Subnet Mask Cheat Sheet
See also RFC 1878.
Hosts Netmask Amount of a Class C
/30 4 255.255.255.252 1/64
/29 8 255.255.255.248 1/32
/28 16 255.255.255.240 1/16
/27 32 255.255.255.224 1/8
/26 64 255.255.255.192 1/4
/25 128 255.255.255.128 1/2
/24 256 255.255.255.0 1
/23 512 255.255.254.0 2
/22 1024 255.255.252.0 4
/21 2048 255.255.248.0 8
/20 4096 255.255.240.0 16
/19 8192 255.255.224.0 32
/18 16384 255.255.192.0 64
/17 32768 255.255.128.0 128
/16 65536 255.255.0.0 256
Subnetting

IP Network Design Sheet
Subnetting

Node IuB UP & CP Addressing (between NodeB and SIU/Router) OAM IP Addressing(between NodeB and SIU/Router)
S.No RBS Name RBS ID
IuB UP/CP subnet
address
IuB UP/CP subnet
mask
IuB UP/CP IP
Address
IuB UP/CP Default
router
IuB UP/CP VLAN ID
OAM subnet
address
OAM Subnet Mask OAM IP Address
OAM Default
Router
OAM VID
1 CGDMG40 1 10.32.160.0 255.255.255.252 10.32.160.1 10.32.160.2 1001 10.32.128.0 255.255.255.252 10.32.128.1 10.32.128.2 2001
2 CGDMG07 2 10.32.160.4 255.255.255.252 10.32.160.5 10.32.160.6 1001 10.32.128.4 255.255.255.252 10.32.128.5 10.32.128.6 2001
3 CGDMG36 3 10.32.160.8 255.255.255.252 10.32.160.9 10.32.160.10 1001 10.32.128.8 255.255.255.252 10.32.128.9 10.32.128.10 2001
4 CGDMG15 4 10.32.160.12 255.255.255.252 10.32.160.13 10.32.160.14 1001 10.32.128.12 255.255.255.252 10.32.128.13 10.32.128.14 2001
5 CGDMG16 5 10.32.160.16 255.255.255.252 10.32.160.17 10.32.160.18 1001 10.32.128.16 255.255.255.252 10.32.128.17 10.32.128.18 2001
6 CGDMG27 6 10.32.160.20 255.255.255.252 10.32.160.21 10.32.160.22 1001 10.32.128.20 255.255.255.252 10.32.128.21 10.32.128.22 2001
7 CGDMG37 7 10.32.160.24 255.255.255.252 10.32.160.25 10.32.160.26 1001 10.32.128.24 255.255.255.252 10.32.128.25 10.32.128.26 2001
8 CGDMG02 8 10.32.160.28 255.255.255.252 10.32.160.29 10.32.160.30 1001 10.32.128.28 255.255.255.252 10.32.128.29 10.32.128.30 2001
9 CGDMG09 9 10.32.160.32 255.255.255.252 10.32.160.33 10.32.160.34 1001 10.32.128.32 255.255.255.252 10.32.128.33 10.32.128.34 2001
10 CGDMG43 10 10.32.160.36 255.255.255.252 10.32.160.37 10.32.160.38 1001 10.32.128.36 255.255.255.252 10.32.128.37 10.32.128.38 2001
11 CGDMG08 11 10.32.160.40 255.255.255.252 10.32.160.41 10.32.160.42 1001 10.32.128.40 255.255.255.252 10.32.128.41 10.32.128.42 2001
12 CGDMG21 12 10.32.160.44 255.255.255.252 10.32.160.45 10.32.160.46 1001 10.32.128.44 255.255.255.252 10.32.128.45 10.32.128.46 2001
ATND Sample
Subnetting

CIDR (Classless inter-domain routing)
CIDR (Classless inter-domain routing) is a method of public IP address assignment. It was introduced in 1993 by
Internet Engineering Task Force with the following goals:
• to deal with the IPv4 address exhaustion problem
• to slow down the growth of routing tables on Internet routers
Before CIDR, public IP addresses were assigned based on the class boundaries:
• Class A – the classful subnet mask is /8.
The number of possible IP addresses is 16,777,216 (2 to the power of 24).
• Class B – the classful subnet mask is /16.
The number of addresses is 65,536
• Class C – the classful subnet mask is /24.
Only 256 addresses available.
Some organizations were known to have gotten an entire Class A public IP address (for example, IBM got all the
addresses in the 9.0.0.0/8 range). Since these addresses can’t be assigned to other companies, there was a
shortage of available IPv4 addresses. Also, since IBM probably didn’t need more than 16 million IP addresses, a lot
of addresses were unused.
To combat this, the classful network scheme of allocating the IP address was abandoned. The new system was
classsless – a classful network was split into multiple smaller networks. For example, if a company needs 12 public
IP addresses, it would get something like this: 190.5.4.16/28.

The number of usable IP addresses can be calculated with the following formula:
2 to the power of host bits – 2
In the example above, the company got 14 usable IP addresses from the 190.5.4.16 – 190.5.4.32
range because there are 4 host bits and 2 to the power of 4 minus 2 is 14. The first and the last
address are the network address and the broadcast address , respectively. All other addresses inside
the range could be assigned to Internet hosts.
CIDR (Classless inter-domain routing)

CIDR blocks
CIDR is principally a bitwise, prefix-based standard for the interpretation of IP
addresses. It facilitates routing by allowing blocks of addresses to be grouped
together into single routing table entries. These groups, commonly called CIDR
blocks, share an initial sequence of bits in the binary representation of their IP
addresses. IPv4 CIDR blocks are identified using a syntax similar to that of IPv4
addresses: a four-part dotted-decimal address, followed by a slash, then a
number from 0 to 32: A.B.C.D/N. The dotted decimal portion is interpreted, like
an IPv4 address, as a 32-bit binary number that has been broken into four
octets. The number following the slash is the prefix length, the number of shared
initial bits, counting from the most significant bit of the address. When
emphasizing only the size of a network, terms like /20 are used, which is a CIDR
block with an unspecified 20-bit prefix.
An IP address is part of a CIDR block, and is said to match the CIDR prefix if the initial N bits of the address and the CIDR
prefix are the same. Thus, understanding CIDR requires that IP address be visualized in binary. Since the length of an IPv4
address has 32 bits, an N-bit CIDR prefix leaves 32-N bits unmatched, meaning that 232-N IPv4 addresses match a given N-
bit CIDR prefix. Shorter CIDR prefixes match more addresses, while longer CIDR prefixes match fewer. An address can
match multiple CIDR prefixes of different lengths.
CIDR is also used with IPv6 addresses and the syntax semantic is identical. A prefix length can range from 0 to 128, due to
the larger number of bits in the address, however, by convention a subnet on broadcast MAC layer networks always has 64-
bit host identifiers. Larger prefixes are rarely used even on point-to-point links.

Assignment of CIDR blocks
The Internet Assigned Numbers Authority (IANA) issues to Regional Internet
Registries (RIRs) large, short-prefix (typically /8) CIDR blocks. For example,
62.0.0.0/8, with over sixteen million addresses, is administered by RIPE NCC,
the European RIR. The RIRs, each responsible for a single, large, geographic
area (such as Europe or North America), then subdivide these allocations into
smaller blocks and issue them to local Internet registries. This subdividing
process can be repeated several times at different levels of delegation. End
user networks receive subnets sized according to the size of their network
and projected short term need. Networks served by a single ISP are
encouraged by IETF recommendations to obtain IP address space directly
from their ISP. Networks served by multiple ISPs, on the other hand, may
often obtain independent CIDR blocks directly from the appropriate RIR.
For example, in the late 1990s, the IP address 208.130.29.33 (since reassigned) was used by www.freesoft.org. An analysis
of this address identified three CIDR prefixes. 208.128.0.0/11, a large CIDR block containing over 2 million addresses, had
been assigned by ARIN (the North American RIR) to MCI. Automation Research Systems, a Virginia VAR, leased an Internet
connection from MCI and was assigned the 208.130.28.0/22 block, capable of addressing just over 1000 devices. ARS used
a /24 block for its publicly accessible servers, of which 208.130.29.33 was one.
All of these CIDR prefixes would be used, at different locations in the network. Outside of MCI's network, the
208.128.0.0/11 prefix would be used to direct to MCI traffic bound not only for 208.130.29.33, but also for any of the
roughly two million IP addresses with the same initial 11 bits. Within MCI's network, 208.130.28.0/22 would become
visible, directing traffic to the leased line serving ARS. Only within the ARS corporate network would the 208.130.29.0/24
prefix have been used.

ARP (Address Resolution Protocol) explained
ARP (Address Resolution Protocol) is a network protocol used to find out the hardware (MAC) address of a
device from an IP address. It is used when a device wants to communicate with some other device on a local
network (for example on an Ethernet network that requires physical addresses to be known before sending
packets). The sending device uses ARP to translate IP addresses to MAC addresses.
The device sends an ARP request message containing the IP address of the receiving device. All devices on a
local network segment see the message, but only the device that has that IP address responds with the ARP
reply message containing its MAC address. The sending device now has enough information to send the packet
to the receiving device.
ARP request packets are sent to the broadcast addresses (FF:FF:FF:FF:FF:FF for the Ethernet broadcasts and
255.255.255.255 for the IP broadcast).

Here is the explanation otf the ARP process:
Let’s say that Host A wants to communicate with host B. Host A knows the
IP address of host B, but it doesn’t know the host B’s MAC address. In
order to find out the MAC address of host B, host A sends an ARP request,
listing the host B’s IP address as the destination IP address and the MAC
address of FF:FF:FF:FF:FF:FF (Ethernet broadcast). Switch will forward
the frame out all interfaces (except the incoming interface). Each device on
the segment will receive the packet, but because the destination IP
address is host B’s IP address, only host B will reply with the ARP reply
packet, listing its MAC address. Host A now has enough information to
send the traffic to host B.
All operating systems maintain ARP caches that are checked before
sending an ARP request message. Each time a host needs to send a
packet to another host on the LAN, it first checks its ARP cache for the
correct IP address and matching MAC address. The addresses will stay in
the cache for a couple of minutes. You can display ARP entries in Windows
by using the arp -a command:

Ping explained
ping is perhaps the most commonly used tool to troubleshoot a network. Ping (Packet Internet
Groper) is included with most operating systems. It is invoked using a ping command and uses
ICMP (Internet Control Message Protocol) to reports errors and provides information related to IP
packet processing. Ping works by sending an ICMP echo request message to the specified IP
address. If the computer with the destination IP address is reachable, it responds with an ICMP
echo reply message.
A ping command usually outputs some other information about a network performance, e.g. a
round-trip time, a time to send an ICMP request packetand receive an ICMP reply packet.
Here is an output of the ping command from Windows 7:
In the example above we have pinged the ip address
10.10.100.1. By default, ping on Windows sends four ICMP
request packets. As you can see from the output above, the host
with the IP address of 10.10.100.1 is reachable and has replied
with four ICMP reply packets. You can also see that the remote
host has replied within 1 ms (time<1ms), which indicates that the
network is not congested.

Traceroute explained
Traceroute is a command-line interface based tool used to identify the path used by a packet to reach its target. This tool
also uses ICMP messages, but unlike ping, it identifies every router in a path taken by the packets. Traceroute is useful
when troubleshooting network problems because it can help identify where exactly the problem is. You can figure out
which router in the path to an unreachable target should be examined more closely as the probable cause of the network’s
failure.
Traceroute sends a series of ICMP echo request packets to a destination. First series of messages has a Time to Live
(TTL) parameter set to 1, which means that the first router in a path will discard the packet and send an ICMP Time
Exceeded message. TTL is then increased by one until the destination host is reached and an ICMP echo reply message
is received. Originating host can then use received ICMP messages to identify all routers in a path.
NOTE
The traceroute command on Windows is named tracert. On Unix and Cisco IOS traceroute it is invoked using the traceroute
command.

Here is an example of using the tracert command in Windows:
In the output above you can see that the
traceroute command has listed the IP
addresses of all of the routers in the path.
Traceroute on Unix-like operating systems
Traceroute command on Unix works slighty
different than the Windows version. It uses
UDP packets with a large destination port
number (33434 to 33534) that is unlikely to
be used by any application at the destination
host. Like the Windows version of the
command, traceroute on Unix uses TTL to get
the IP addresses of the intermediary routers.
When a destination host is reached, it replies
with an ICMP port unreachable message.

Some of the protocols included in the TCP/IP suite are:
 ARP (Address Resolution Protocol)
used to associate an IP address with a MAC address.
 IP (Internet Protocol)
used to deliver packets from the source host to the destination host based on the IP addresses.
 ICMP (Internet Control Message Protocol)
used to detects and reports network error conditions. Used in ping.
 TCP (Transmission Control Protocol)
a connection-oriented protocol that enables reliable data transfer between two computers.
 UDP (User Datagram Protocol)
a connectionless protocol for data transfer. Since a session is not created before the data transfer,
there is no guarantee of data delivery.
 FTP (File Transfer Protocol)
used for file transfers from one host to another.
 Telnet (Telecommunications Network)
used to connect and issue commands on a remote computer.
 DNS (Domain Name System)
used for host names to the IP address resolution.
 HTTP (Hypertext Transfer Protocol)
used to transfer files (text, graphic images, sound, video, and other multimedia files) on the World Wide
Web.

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