IP addresses explain the format of an IP address and how an IP address is associated with a device on a network

IP addresses

IP address - a unique software address used to communicate over the internet.

Every device on the internet has a unique IP address. 
IP addresses are either 32-bit numbers. 
The address  is broken down into four 8-bit numbers (each is called an octet) (standard IPv4). 
Each octet can represent a number between 0 and 255 and is separated by a full stop, eg

Equivalent for 11000000 10101000 00000001 00000101 is
Each IP address has two parts. How do nodes determine where the network portion is and where is the node address? The subnet mask is used for this.

Subnet mask

A 32-bit IP address mask that indicates the number of bits of an IP address reserved for a subnet address.

In the subnet mask, ones correspond to the network portion and zeros to the host address.

For example,

if IP address and subnet mask, 

IP address 192 168 1 20
Subnet mask 255 255 255 0

then 20 - host address is in the network 192.168.1

Classes of IP addresses

Class The first octet Subnet mask Number of netrorks and hosts
A 1-127


networks 126 (27-2)
hosts 16 777 214 (224-2)

B 128-191


networks 16 382 (214-2)
hosts 65 534 (216-2)

C 192-223


networks 2 097 150 (221-2)
hosts 254 (28-2)

D 224-239 Reserved for multicast groups.  
E 240-255 Reserved for future use, or research and development purposes.  

Private and public IP addresses

A private IP address, also called internal, intranet, or local, is an IP address that belongs to a special range not used on the Internet. Such addresses are intended for use in local networks, the distribution of such addresses is not controlled by anyone.

IP address range Classful description – single class A network – 16 contiguous class B networks – 256 contiguous class C networks

All other addresses are public addresses.


IPv6 addresses consist of 8 groups of 16-bit hexadecimal values separated by colons (:). IPv6 addresses have the following format:


Each aaaa is a 16-bit hexadecimal value, and each a is a 4-bit hexadecimal value. Following is a sample IPv6 address:


or 3FFE:0:0:1:200:F8FF:FE75:50DF

IPv6 has three types of addresses:

  • Unicast—For a single interface.
  • Multicast—For a set of interfaces on the same physical medium. A packet is sent to all interfaces associated with the address.
  • Anycast—For a set of interfaces on different physical media. A packet is sent to only one of the interfaces associated with this address, not to all the interfaces.

More about IPv6

Формула расчета сетей


  1. Explain the purpose of IP address.
  2. How many bits are used to store an IP address?
  3. What are the two parts of an IP address?
  4. What is the subnet mask used for?


Ex. 1

Ex. 2

Exam questions:


Категория: Internet technology | Добавил: bzfar77 (04.05.2021)
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