How To Calculate Valid Host in Subnetting

Subnetting is a fundamental skill for network administrators and IT professionals. This helps them manage and organize IP addresses within a network.

One important aspect of subnetting is calculating valid hosts within a subnet. In this post, I will show you How To Calculate Valid Host in Subnetting.

Basics of subnetting

Before we go into calculating valid hosts, let’s review some essential concepts:

  1. IP Address Structure: IP addresses are composed of two parts: the network portion and the host portion. The division between these portions is determined by the subnet mask.
  2. Subnet Masks: Subnet masks define how an IP address is divided into network and host parts. They consist of 32 bits(for IPV4) divided into two parts: the leftmost bits represent the network, and the rightmost bits represent the hosts.
  3. CIDR Notation: The CIDR (Classless Inter-Domain Routing) notation is commonly used to express IP addresses and their associated routing prefix. It’s represented as IP_address/prefix_length (e.g.,
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How to Calculate a Valid Host in Subnetting

Here are the steps to calculate a valid host in subnetting.

Step 1: Identify the Network Address

Given an IP address and subnet mask, the network address is obtained by performing a bitwise AND operation between the IP address and the subnet mask.


IP Address:
Subnet Mask: (or /24 in CIDR notation)
Network Address:

Step 2: Determine the Broadcast Address

The broadcast address is the highest address within the subnet. To find it, flip all the host bits in the subnet and perform a bitwise OR operation with the network address.

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Network Address:
Inverted Subnet Mask:
Broadcast Address:

Step 3: Calculate the Usable Host Range

Once you have the network and broadcast addresses, you can determine the valid host range by excluding these two addresses.


Network Address:
Broadcast Address:
Usable Host Range: to

How to find first valid host on a subnetwork

The first valid host in a subnetwork is obtained by adding 1 to the network address. In the case of a network with a network address of

 First Valid host = + 1 =

How to find last valid host on a subnetwork

The last last valid host in a subnetwork is obtained by subtracting 1 from the broadcast address. In the case of a network with a broadcast address of,

Last valid host = - 1 =

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