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```									21-IP addressing

Dr. John P. Abraham
Professor
UTPA
Chapters 19, 20
• I have already covered these concepts
elsewhere.
• Physical
• Logical
• 32 bits
– Hierarchy – prefix and suffix
– Prefix identifies the network – given by IANA
first address in the block) is the one that is
assigned to the organization. The range of
addresses can automatically be inferred from the

– Suffix identifies the computer –given locally
– No two computers can have the same public IP
• Divided IP address space into three
primary classes A, B, C and also there
exist class D (multicasting) and E.
• First four (MSB) bits will determine its
class
Lea    Size of     Size of    Number     Addresse       Start      End
Bits   Number        Bit     Networks      per            s
Bit field    field                Network

Class A         0      8           24         128        16,777,     0.0.0.0   127.255.
7                24
(2 )        216 (2 )                255.255

Class B        01      16          16        16,384      65,536      128.0.0. 191.255.
14          16
(2 )        (2 )          0        255.255

8
Class C       110      24          8         2,097,1     256 (2 )    192.0.0. 223.255.
21
52 (2 )                   0        255.255

Class D       1110     not         not       not         not         224.0.0. 239.255.
(multicast)          defined     defined   defined     defined       0        255.255

Class E       1111     not         not       not         not         240.0.0. 255.255.
(reserved)           defined     defined   defined     defined       0        255.255
Figure 4.5   Finding the class in decimal notation
Find the class of each address:
a. 227.12.14.87      b.193.14.56.22       c.14.23.120.8
d. 252.5.15.111       e.134.11.78.56

Solution
a. The first byte is 227 (between 224 and 239); the class is D.
b. The first byte is 193 (between 192 and 223); the class is C.
c. The first byte is 14 (between 0 and 127); the class is A.
d. The first byte is 252 (between 240 and 255); the class is E.
e. The first byte is 134 (between 128 and 191); the class is B.

• The network address is the beginning
address of each block. It can be found by
applying the default mask to any of the
addresses in the block (including itself). It
retains the netid of the block and sets the
hostid to zero.
Example 12

Solution
The default mask is 255.0.0.0, which means that only the first
byte is preserved and the other 3 bytes are set to 0s. The
Example 15

200.45.34.56 and the subnet mask is 255.255.240.0?

Solution
We apply the AND operation on the address and the subnet
Address            ➡ 11001000 00101101 00100010 00111000
Subnet Mask        ➡ 11111111 11111111 11110000 00000000
Subnetwork Address ➡ 11001000 00101101 00100000 00000000.