Network Address Broadcast Address and IP Address Explained

This tutorial explains network address, broadcast address and IP address with examples. Learn what network address is, types of network address, how to find the default network address & broadcast address of any IP class along with network addressing such as unicast, multicast and broadcast in details.

IP Address

An IP address is a unique identity of an interface in IP network. IP addresses are just like postal addresses. In order to send and receive packages through postal system, every house needs a unique postal address. Just like it, in order to send and receive IP packets, every interface needs a unique IP address in IP network.

IP address format

An IP address consists 32 bits. These bits are divided in four equal sections. Sections are separated by periods and written in a sequence.

ip address example

In measurement, 8 bits are equal to one byte or octet. So we can also say an IP address consists four bytes or octets separated by periods.

Two popular notations are used for writing an IP address, binary and decimal.

In binary notation, all four sections are written in binary format. For example, few IP addresses in binary format are listed below.

00001010.00001010.00001010.00001010
10101100.10101000.00000001.00000001
11000000.10101000.00000001.00000001

In decimal notation, all four sections are written in decimal format. A decimal equivalent value of the octet is used in each section. For example, IP addresses from above example are listed below in decimal format.

10.10.10.10
172.168.1.1
192.168.1.1

In real life you rarely need to write an IP address in binary format. But if you are preparing for any Cisco exam, I highly recommend you to learn the binary format along with decimal format. Nearly all Cisco exams include questions about IP addresses. Learning both binary and decimal notations will help you in solving IP addressing related questions more effectively.

IP address components

As we discussed earlier, an IP address is just like a postal address. Whether it is a postal address or an IP address, it contains two addresses, group address and individual address. In a particular group, the group address is common for all members and the individual address is unique for each member.

In postal system, group address and individual addresses are known as area address and house addresses. While in IP network, these addresses are known as network address and host addresses respectively.

Following figure shows few examples of addresses from both postal system and IP network.

network address examples

Subnet Mask

In an IP address, how many bits are used in network address and how many bits are left for host address is determined by a subnet mask. Just like an IP address, subnet mask is also a 32 bits long address and can be written in both binary and decimal notations.

Examples of subnet mask in binary notation are following: -

11111111.00000000.00000000.00000000
11111111.11111111.00000000.00000000
11111111.11111111.11111111.00000000

Examples of subnet mask in decimal notation are following: -

255.0.0.0
255.255.0.0
255.255.255.0

IP address and subnet mask are always used together. Without IP address, subnet mask is just a number and vice versa. Few examples of writing IP address in correct way are listed below.

Examples of IP address with subnet mask in binary format

00001010.00001010.00001010.00001010
11111111.00000000.00000000.00000000

10101100.10101000.00000001.00000001
11111111.11111111.00000000.00000000

11000000.10101000.00000001.00000001
11111111.11111111.11111111.00000000

Examples of IP address with subnet mask in decimal format

10.10.10.10
255.0.0.0

172.168.1.1
255.255.0.0

192.168.1.1
255.255.255.0

IP classes

There are 4,294,967,296 IP addresses. Based on following rules, IP addresses are categorized in five classes; A, B, C, D and E.

  • In class A, first bit of the first byte always remains off (0).
  • In class B, first bit of first byte always remains on and the second bit of the first byte always remains off.
  • In class c, first two bits of first byte always remain on and the third bit of the first byte always remains off.
  • In class d, first three bits of first byte always remain on and the fourth bit of the first byte always remains off.
  • In class d, first four bits of first byte always remain on and the fifth bit of the first byte always remains off.

By turning all remaining bits of the first byte on, we can get the first IP address of that class. Exactly same way by turning all remaining bits of the first byte off, we can get the last IP address of that class.

Class Starting bit(s) in binary Decimal Value of first octet in range
A 0 0 to 127
B 10 128 to 191
C 110 192 to 223
D 1110 224 to 239
F 11110 239 to 255

Class of an IP address is determined by the value of first byte or octet.

  • If value in first byte is in range 0 to 127, it is a Class A address.
  • If value in first byte is in range 128 to 191, it is a Class B address.
  • If value in first byte is in range 192 to 223, it is a Class C address.
  • If value in first byte is in range 224 to 239, it is a Class D address.
  • If value in first byte is in range 240 to 225, it is a Class E address.
Class Starting Address Ending Address Subnet mask
A 0.0.0.0 127.255.255.255 255.0.0.0
B 128.0.0.0 191.255.255.255 255.255.0.0
C 192.0.0.0 223.255.255.255 255.255.255.0
D 224.0.0.0 239.255.255.255 Not applicable
E 240.0.0.0 255.255.255.255 Not applicable

Although we have nearly 4.3 billion IP addresses but not all are available for end devices. From these addresses, following addresses are reserved and cannot be assigned to end devices.

0.0.0.0:- This address represents all networks.

127.0.0.0 to 127.255.255.255: - This IP range is reserved for loopback testing.

224.0.0.0 to 239.255.255.255(Class D): - This IP class is reserved for multicast.

240.0.0.0 to 255.255.255.254(Class E): - This IP class is reserved for future use.

255.255.255.255: - This address represents all hosts.

Besides these reserved address, we also cannot use the first and the last IP address of each network. First IP address is reserved for the network address and last IP address is reserved for the broadcast address. We can use only the addresses available between the network address and the broadcast address for end devices.

IP address vs Network Address

As discussed, an IP address is a combination of two separate addresses, network address and host address. If we exclude host address from IP address, we will get network address. In simple term, a network address is an IP address without host address. In technical term, a network address is an IP address in which all host bits are turned off.

We can only turn on or off host bits. We cannot turn on or off reserved network bits. In class A, B and C first 8, 16 and 24 bits are reserved respectively for network addresses.

network portion and host portion in ip address

IP address vs Host Address

Any IP operation such as building a network address or host address and Subnetting are always performed in the host portion of an IP address. We can turn of and off host bits as per our requirement. In class A, B and C last 24 bits, 16 bits and 8 bits are defined as host bits respectively.

Private IP addresses vs Public IP addresses

In class A, B and C following IP addresses are defined as private IP addresses:-

In class A: - 10.0.0.0 to 10.255.255.255

In class B: - 172.16.0.0 to 172.31.255.255

In class C: - 192.168.0.0 to 192.168.255.255

Except private IP addresses and reserved IP addresses, all remaining IP addresses of Class A, B and C are considered as public IP addresses.

Public IP addresses are used in public network such as Internet. Public IP addresses are maintained and regulated by ICANN (Internet Corporation for Assigned Names and Numbers).

Private IP addresses are used in private network. Private IP addresses are locally significant and not routable in public network.

Network addressing

There are three types of network address; unicast, multicast and broadcast.

Unicast address

Unicast address represents an individual end device. If an IP packet is sent on a unicast address, it is intended only for that particular recipient. Unicast addresses are usually used by end devices for end to end communication.

network address unicast example

Multicast address

Multicast address represents a group of devices. If an IP packet is sent on a multicast address, it is intended for all members of that group. Multicast addresses are usually used by networking devices for running their own services.

network address multicast example

Broadcast address

Broadcast address represents all devices of the network. If an IP packet is sent on a broadcast address, it is intended for all devices of that network. Broadcast addresses are usually used to locate hosts or services in network.

network address broadcast example

The differences between multicast address and broadcast address are following: -

Multicast address represents only a group of devices from a particular network while broadcast address represents all devices of that particular network.

Based on configuration, messages which are sent on a multicast address are normally allowed to pass through the router. Messages which are sent on a broadcast address are not allowed to pass through the router under any circumstances.

That’s all for this tutorial. If you have any suggestion, feedback or comment about this tutorial, please let me know. If you like this tutorial, please don’t forget to share it through your favorite social platform.

ComputerNetworkingNotes CCNA Study Guide Network Address Broadcast Address and IP Address Explained