Ip basics

IP Addressing & Subnetting
Made Easy
Developed By
Md Mahmudur Rahman Lanin
MiKroTik Listed Consultant
B.Sc in CSE
G.M (Technical Department)
Bijoy Online Ltd.
____________________________________________________________
MTCNA, MTCRE, CCNA, CCNP, RHSE
1Developed By Lanin

Working with IP
Addresses
2Developed By Lanin

Developed By Lanin 3
Introduction
1. You can probably work with decimal
numbers much easier than with the
binary numbers needed by the
computer.
2. Working with binary numbers is time-
consuming & error-prone.

Octets
 The 32-bit IP address is broken up
into 4 octets, which are arranged into
a dotted-decimal notation scheme.
 An octet is a set of 8 bits & not a
musical instrument.
Example of an IP version 4:
172.64.126.52

Thinking in Binary
A.The binary system uses only 2 values
“0 & 1” to represent numbers in
positions representing increasing
powers of 2.
B.We all are accustomed to thinking &
working in the decimal system, which
is based on the number 10.

Thinking in Binary (Cont.)
A.To most humans, the number 124
represents 100 + 20 + 4.
B.To the computer, this number is
1111100, which is 64 (26) + 32 (25)
+ 16 (24) + 8 (23) + 4 (22) + 0 + 0

 Each position in a binary
number represents, right to left,
a power of two beginning with 20
& increasing by one power as it
moves left: 20, 21, 22, 24, etc.

Converting to Decimal
1. You’ll need to convert binary to decimal &
vice versa to compute subnets & hosts.
2. So, it’s time for a quick review lesson in
binary-to-decimal conversion.
3. There are 8 bits in an octet & each bit can
only be a 1 or a 0.

Converting to Decimal (Cont.)
 What then do you suppose is the largest
decimal number that can be expressed in an
octet?
Eight 1’s (1111 1111)

27 26 25 24 23 22 21 20
1 1 1 1 1 1 1 1
128 64 32 16 8 4 2 1
A.Now, for double the money, what is its
equivalent decimal value?
The binary number 1111 1111 converts into the decimal number:
128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255

1. Therefore, the largest decimal
number that can be stored in an IP
address octet is 255.
2. The significance of this should
become evident later in this
presentation.

IPAddress Classes
1.IP addresses are divided into 5 classes,
each of which is designated with the
alphabetic letters A to E.
2.Class D addresses are used for
multicasting.
3.Class E addresses are reserved for
testing & some mysterious future use.

IPAddress Classes (Cont.)
The 5 IP classes are split up based on the
value in the 1st octet:

IPAddress Classes (Cont.)
Using the ranges, you can determine
the class of an address from its 1st octet
value.
An address beginning with 120 is a
Class A address, 155 is a Class B
address & 220 is a Class C address.

Are You the Host or the
Network?
 The 32 bits of the IP address are divided into
Network & Host portions, with the octets assigned
as a part of one or the other.
Network & Host Representation
By IP Address Class
Class Octet1 Octet2 Octet3 Octet4
Class A Network Host Host Host
Class B Network Network Host Host
Class C Network Network Network Host

Network? (Cont.)
 Each Network is assigned a network address
& every device or interface (such as a router
port) on the network is assigned a host
address.
 There are only 2 specific rules that govern the
value of the address.

Network? (Cont.)
 A host address cannot be designated by
all zeros or all ones.
 These are special addresses that are
reserved for special purposes.

Class A Addresses
 Class A IP addresses use the 1st 8 bits (1st Octet)
to designate the Network address.
 The 1st bit which is always a 0, is used to
indicate the address as a Class A address & the
remaining 7 bits are used to designate the
Network.
 The other 3 octets contain the Host address.

Class A Addresses (Cont.)
 There are 128 Class A Network
Addresses, but because addresses with
all zeros aren’t used & address 127 is a
special purpose address, 126 Class A
Networks are available.

 There are 16,777,214 Host addresses
available in a Class A address.
 Rather than remembering this number
exactly, you can use the following formula
to compute the number of hosts available in
any of the class addresses, where “n”
represents the number of bits in the host
portion:
(2n – 2) = Number of available hosts

 For a Class A network, there are:
224 – 2 or 16,777,214 hosts.
 Half of all IP addresses are Class A
addresses.
 You can use the same formula to
determine the number of Networks in an
address class.
 Eg., a Class A address uses 7 bits to
designate the network, so (27 – 2) = 126 or
there can be 126 Class A Networks.

Class B IP Addresses
 Class B addresses use the 1st 16 bits (two
octets) for the Network address.
 The last 2 octets are used for the Host
address.
 The 1st 2 bit, which are always 10,
designate the address as a Class B
address & 14 bits are used to designate
the Network. This leaves 16 bits (two
octets) to designate the Hosts.

Class B IP Addresses (Cont.)
 So how many Class B Networks can there
be?
 Using our formula, (214 – 2), there can be
16,382 Class B Networks & each Network
can have (216 – 2) Hosts, or 65,534 Hosts.

Class C IP Addresses
 Class C addresses use the 1st 24 bits
(three octets) for the Network address &
only the last octet for Host addresses.the
1st 3 bits of all class C addresses are set to
110, leaving 21 bits for the Network
address, which means there can be
2,097,150 (221 – 2) Class C Networks, but
only 254 (28 – 2) Hosts per Network.

Class C IP Addresses (Cont.)

Special Addresses
 A few addresses are set aside for specific
purposes.
 Network addresses that are all binary
zeros, all binary ones & Network
addresses beginning with 127 are special
Network addresses.

Special Addresses (Cont.)

 Within each address class is a set of
addresses that are set aside for use in
local networks sitting behind a firewall or
NAT (Network Address Translation)
device or Networks not connected to the
Internet.

 A list of these addresses for each IP
address class:

Subnet Mask
 An IP address has 2 parts:
 The Network identification.
 The Host identification.
 Frequently, the Network & Host portions of
the address need to be separately
extracted.
 In most cases, if you know the address class,
it’s easy to separate the 2 portions.

Subnet Mask (Cont.)
 With the rapid growth of the internet &
the ever-increasing demand for new
addresses, the standard address class
structure has been expanded by
borrowing bits from the Host portion to
allow for more Networks.
 Under this addressing scheme, called
Subnetting, separating the Network &
Host requires a special process called
Subnet Masking.

Subnet Mask (Cont.)
 The subnet masking process was
developed to identify & extract the
Network part of the address.
 A subnet mask, which contains a binary
bit pattern of ones & zeros, is applied to
an address to determine whether the
address is on the local Network.
 If it is not, the process of routing it to an
outside network begins.

Subnet Mask (Cont.)
 The function of a subnet mask is to
determine whether an IP address exists
on the local network or whether it must
be routed outside the local network.
 It is applied to a message’s destination
address to extract the network address.
 If the extracted network address
matches the local network ID, the
destination is located on the local
network.

Subnet Mask (Cont.)
 However, if they don’t match, the
message must be routed outside the
local network.
 The process used to apply the subnet
mask involves Boolean Algebra to filter
out non-matching bits to identify the
network address.

Boolean Algebra
 Boolean Algebra is a process that applies
binary logic to yield binary results.
 Working with subnet masks, you need
only 4 basic principles of Boolean
Algebra:
 1 and 1 = 1
 1 and 0 = 0
 0 and 1 = 0
 0 and 0 = 0

Boolean Algebra (Cont.)
 In another words, the only way you can
get a result of a 1 is to combine 1 & 1.
Everything else will end up as a 0.
 The process of combining binary values
with Boolean Algebra is called Anding.

Default Standard Subnet Masks
 There are default standard subnet masks
for Class A, B and C addresses:

A Trial Separation (Cont.)
 The subnet mask goes like this:
1. If a destination IP address is
206.175.162.21, we know that it is a
Class C address & that its binary
equivalent is:
11001110.10101111.10100010.00010101

2. We also know that the default standard
Class C subnet mask is: 255.255.255.0
and that its binary equivalent is:
11111111.11111111.11111111.00000000

3. When these two binary numbers (the IP
address & the subnet mask) are
combined using Boolean Algebra, the
Network ID of the destination network is
the result:

Configuring an IP Address (Cont.)
 The IP Address command is entered from
the config-if mode because the action
affects only that interface.
 Both the IP address & the subnet mask
are defined in the command.

Verifying an IP Address
 IP addresses are verified using PING,
Trace &Telnet.
 It is important that you know that PING
is used to verify IP address connections
to the Network Layer & thatTelnet is
used to verify network IP address
connections to the Application Layer.

Verifying with Telnet
 The reason you need to verify IP
addresses is to ensure that the various
parts of a network can properly
communicate with the other parts.
 Eg., if you canTelnet (Terminal
Emulation Protocol) into a router from a
remote location on the same network,
you can verify that the interface & route
are up and available.

Verifying with Telnet (Cont.)
 BecauseTelnet operates on the OSI
Model’s Application Layer, when it’s
functioning, it’s safe to assume that all
lower layers are also functioning.

Verifying with PING
 The PING (Packet Internet Groper)
command verifies OSI Layer 3 (Network
Layer) connectivity.
 It sends out ICMP (Internet Control
Message Protocol) messages to verify
both the logical addresses & the Physical
connection.

Verifying with PING (Cont.)
 The PING command issued from a Cisco router
responds with a number of single character
responses.

Verifying with Traceroute
 TheTraceroute orTrace command is used
to show the complete route from a
source to a destination.
 Trace sends out probe packets one at a
time to each router or switch in the path
between the source & the destination IP
address entered.

Verifying with Traceroute (Cont.)
 Traceroute displays the round-trip time
for each packet sent to each upstream
router.
 Traceroute has really only 2 results:
 Time exceeded or
 Destination unreachable.
 Trace is used to determine where a
breakdown in a route may be occurring.

 Example on howTrace is used:
 A network has 4 routers (A, B, C & D). A
Trace command is issued on router A to trace
the route from itself to router D.
 A timing response comes back from router B,
but the next message indicates that router C
is unreachable. You can be fairly certain that
the problem lies somewhere on the route
between router B & router C.

 Like PING,Trace has its own set of
response codes:

Ip basics

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