Category - IP Addressing

IP Addressing step by step

IPv4 addresses

  • Consist of 32 bits.
  • Are broken into four octets (8 bits each).
  • Use dotted-decimal format; an example is
  • Minimum value (per octet) is 0, and the maximum value is 255.
  • is a network ID.
  • is a broadcast IP.

IPv4 Address Classes

TABLE FF.13IPv4 Address Classes
First OctetSecond OctetThird OctetFourth Octet
Class ANetworkHostHostHost
Class BNetworkNetworkHostHost
Class CNetworkNetworkNetworkHost

TCP/IP defines two additional address classes:

  • Class D: Used for multicast addresses.
  • Class E: Used for research purposes.

ip address

TABLE FF.14 Address Class Ranges

Class                                    First Octet Decimal Range

A                                              1 to 126

B                                             128 to 191

C                                             192 to 223

D                                             224 to 239

E                                              240 to 255

The 127.x.x.x address range is reserved for loopback addresses.

Default subnet masks:

  • ¬†Class A:
  • Class B:
  • Class C:

Classless Addressing

Classless Interdomain Routing (CIDR) notation might also be used to identify the subnet mask. The CIDR notation for each network class can be determined by counting the 1s in binary or the number of bits that make up the network portion of the address.

The mask is written in slash notation as follows:

  • Class A: /8
  • Class B: /16
  • Class C: /24

Private Ranges

IANA private address space allocations:

  • Class A: to
  • Class B: to
  • Class C: to


TABLE FF.15 Decimal to Binary Conversions

ClassFirst Octet Decimal Range

To calculate the hosts in a subnet, we can use the formula 2H ‚Äď 2. The exponent H represents the number of host bits in a network.

To calculate the networks in a subnet, we can use the formula 2N ‚Äď 2. The exponent N repre¬≠sents the number of subnet bits in a network.

The range of valid IP addresses in a subnet is the first IP address after the Network ID and the last IP address before the broadcast IP address.

The following represents IP subnetting: IP address =

Subnet mask =

Network ID =

Broadcast IP =

Valid IP range = to


IPv6 is a workable IP version that was created in the event that the IP space from IPv4 is exhausted.

IPv6 address format summary:

  • Defined by RFC 2373 and RFC 237.
  • Consists of 128 bits, with a 64-bit network prefix and a 64-bit local identifier.
  • Represented by 32 hexadecimal digits broken into eight smaller groups of four.
  • Utilizes CIDR notation (slash notation) to discern a subnet range, so you might see the same IP address subnetted and written out as

2001 :0BD2:0200:08F1 :0000:0000:0000: 16AB/16.

The same IPv6 IP address can be written out in all of the following ways: 2001 :0BD2 :0200:08F1 :0000:0000:0000: 16AB

200 1:BD2 :200:8F1 :0:0:0:16AB

200 1:BD2 :200:8F1 ::16AB


Types of IPv6 Addresses

1. Link-local addresses: Addresses that have the shortest reach of the IP address types. They can only go as far as the Layer 2 domain. These addresses are autogenerated with or without the use of a DHCP server. So, when an IPv6 node goes online, this address is assigned automatically.

2. Unique/site-local addresses: Addresses that have a broader scope than link-local addresses. They can expand to the size of an organization and are used to describe the boundary of the organizational network. These are the private addresses for IPv6.

3.¬†Global addresses: Addresses that have the broadest scope of all. As the name indi¬≠cates, these addresses are for global use‚ÄĒthat is, for Internet communications.

4. Multicast: Addresses that are extremely important because of their use in group com­munications and broadcast messaging.

Integrating IPv4 and IPv6

There are several ways to integrate IPv4 and IPv6 addressing. You can implement dual-stack,tunneling, or translation techniques to help IPv4 and IPv6 addresses exist together on the net-work simultaneously.

IP Addressing

IP address is a unique identifier of a computer on TCP/IP networks and on the internet.  Every computer requires a unique IP address to be a part of the internet and the IP address is provided by the internet service providers.  Every IP address consists of the 32 bits and a binary system of 0s and 1s.  The binary number system consist of only two types of digits 0 and 1. It is easier for us to remember the decimal numbers rather than the binary number system such as 011001101. On a same network segment, all the IP address share the same network address.

There are five classes of the IP addresses such as A, B, C, D and E and only 3 classes are in the use. Class D IP addresses are reserved for the multicast group ant cannot be assigned to hosts and the E class IP addresses are the experimental addresses and cannot be assigned to the people. Every IP address consists of 4 octets and 32 bits.  Every participating host and the devices on a network such as servers, routers, switches, DNS, DHCP, gateway, web server, internet fax server and printer have their own unique addresses within the scope of the network.

TCP/IP protocols are installed by default with the Windows based operating systems. After the TCP/IP protocols are successfully installed you need to configure them through the Properties Tab of the Local Area Connection.

IP Addresses Classes

Class A

The binary address for the class A starts with 0. The range of the IP addresses in the class A is between 1 to 126 and the default subnet mask of the class A is  Class A supports 16 million hosts on each of 125 networks.  An example of the class A is  Class A is used for the large networks with many network devices.

Class B

The binary address for the class B starts with 10. The range of the IP address in the class B is between 128 to 191 and the default subnet mast for the class B is  Class B supports 65,000 on each of 16,000 networks. An example of the class B address is  Class B addresses scheme is used for the medium sized networks.

Class C

The binary address for the class C starts with 110. The range of the IP addresses in the class C is between 192 to 223 and the default subnet mask for the class C is 255.255.255.  Class C hosts 254 hosts on each of 2 million networks.  An example of the Class C IP address is  Class C is used for the small networks with less then 256 devices and nodes in a network.

Class D

The binary addresses for the class D starts with 1110 and the IP addresses range can be between 224 to 239.  An example of the class D IP address is

Class E

The binary address can starts with 1111 and the decimal can be anywhere from 240 to 255.  An example of the class E IP address is

It is very important to know that all the computers in the same network segment should have the IP addresses for the same class i.e. form A, B or C

IP Addressing

IP Addressing Tips 

  • A Network ID cannot be All 0s
  • A host ID cannot be All 1 because this represents a broadcast address for the local network.
  • Each host must have a unique host portion of the IP address.
  • All hosts on the same network segment should have the same network id.
  • A host address cannot be 127 because 127 has been reserved for the loop back functionalities.

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