Computer Network Architecture
Lecture 9:
IP Addressing
13/1/2013
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IP Address
• An IP address is a 32-bit, two-level hierarchical number.it is
uniquely defined by a network layer address.
• It is hierarchical because the first portion of the address
represents the network, and the second portion of the address
represents the node (or host).
• The 32 bits are grouped into four octets, with 8 bits per octet.
The value of each octet ranges from 0 to 255 decimal, or
00000000 to 11111111 binary. IP addresses are usually written in
dotted decimal notation, which means that each octet is written in
decimal notation and dots are placed between the octets.
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IP Address (Con.)
• The hosts of an network have identical bit
patterns in the network address portion of their
IP addresses.
• In the following example, the two addresses have
identical network portions. Therefore, hosts
assigned these two addresses would be on the
same logical network:
172.16.4.20
172.16.4.32
network host
network host
portion portion
portion portion
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IP Address(Con.)
• Although, IP addresses are divided into two parts (network, host) portion,
the number of bytes for each of them are different.
• The decision of how many bits are required for the host portion are depend
on the number of hosts that a network requires.
• For example, If a particular network requires at least 200 hosts, you would
need to use enough bits in the host portion to be able to represent at least
200 different bit patterns.
• To assign a unique address to 200 hosts, you would use the entire last
octet. With 8 bits, a total of 256 different bit patterns can be achieved. As
with the previous example, this means that the bits for the upper three
octets represent the network portion.
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Converting IP Addresses Between Decimal and
Binary
• The IP address can be decimal or binary. we can convert
between of them.
•
Value for each bit.
1+ 2+ 4+ 8+ 16+ 32+ 64+ 128= 255
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Converting IP Addresses Between Decimal
and Binary
• Converting From Binary to Decimal
0
1
0
0 0
0
0
1
128 64 32 16 8
4
2
1
0 + 64+ 0 + 0+ 0 + 0 + 0 + 1= 65
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Converting IP Addresses Between Decimal and
Binary
• Examples: find the decimal addresses for the
following binary addresses:
• 00001010 00000001 00010111 00010011
• 10101010 01000001 00010010 10101100
• 11000000 10101000 00001110 11111111
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Converting IP Addresses Between Decimal
and Binary
• Examples: find the binary addresses for the
following decimal addresses:
• 10.1.23.19
• 192.168.14.6
• 172.18.65.170
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Thank You
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