CCNA Exam: 192.168.10.0 Subnetting - Usable Host Calculation

# Subnetting: 192.168.10.0 with Subnet Mask 255.255.255.240

### Question

How many usable host are there per subnet if you have the address of 192.168.10.0 with a subnet mask of 255.255.255.240?

### Explanations

Click on the arrows to vote for the correct answer

A. B. C. D.

D

The subnet mask 255.255.255.240 is a Class C subnet mask, which means the first 3 octets (24 bits) are fixed and the last octet (8 bits) is used for defining the subnet and host addresses.

To determine the number of usable hosts per subnet, you need to calculate the number of valid host addresses within the subnet.

Given the IP address 192.168.10.0 and a subnet mask of 255.255.255.240, we can analyze the subnet mask to determine the number of host bits.

The subnet mask 255.255.255.240 can be represented in binary as:

11111111.11111111.11111111.11110000

Counting the number of zeros in the subnet mask, we find that there are four zeros. Each zero represents a bit that can be used for host addressing.

The number of usable host addresses can be calculated using the formula: 2^n - 2, where 'n' represents the number of host bits.

In this case, 'n' is equal to 4 (the number of zeros in the subnet mask).

Calculating: 2^4 - 2 = 16 - 2 = 14

So, there are 14 usable host addresses per subnet.

Therefore, the correct answer is D. 14.