IP Addressing: –

IP addressing in network area we consider as a unique string of numbers separated by full stops that identifies each computer using the Internet Protocol to communicate over a network. It is very useful in internet, when we want to share information with each other. It is used by many people in their networks but sometimes it is difficult to identify the addresses which either reserved or already used for broadcast etc. This times, We bring you some important ip addresses which should be known by the person who want to go for CCNA or pursue career in network field.


1) When all the net id as well as host id portion bits of an IP address are zero then the address reserve for default routing. It is invalid IP address.

For e.g.: –              0       .       0      .       0       .       0


Net id                    Host id


2) When all the host id  portion bits of an IP address are zero then it represent the Network address. It also invalid IP address.


Class A            1       .       0       .       0      .       0


Net id                      Host id

10      .       0      .       0       .      0


Net id                     Host id


Class B           128    .       0       .       0       .      0


Net id                      Host id

172    .       0       .      0       .      0


Net id                      Host id


Class C             192    .       0      .        0      .      0


Net id                     Host id


3) When all the host id portion bits are one then it represent the Broadcast address. It is also invalid IP address.

For e.g.: –

Class A               1       .      255   .       255   .    255


Net id                      Host id


Class B              128    .      255    .      255    .   255


Net id                      Host id


Class C                 192.       168    .        1      .    255



4) Loopback or self-testing address: – It is use for self-testing of LAN card. It is use for test TCP/IP setting.

For Example.   to

The IP Address is also known as Localhost for Internal Server Server .


5) APIPA (Automatic Private Internet Protocol Address)

It is stand and generated by client PC automatically. When DHCP server is not available or DHCP server is busy in a network. These IP address are used to stop the unusual broadcasting. Communication is possible but only within LAN. APIPA is valid IP address.

For Example. to


6) Private IP Address

  •    It is also called non routable address.
  •    Internet is doesn’t run on private IP address.
  •    It is free of cost. It is not use in WAN network.
  •    Use to avoid the wastage of public IP address.
  1.       to
  2.   to
  3. to




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Valid IP Addressing vs Invalid IP Addressing

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