For example, deserve to you prize this question that essentially asks “how plenty of hosts?”

Bart is designing a network segment the only needs 24 IP addresses assigned. He needs to conserve the IP attend to space. What CIDR notation is the BEST an option for this network?

A. /25

B. /26

C. /27

D. /28

You are watching: How many subnets do you get with a subnet of 192.168.1.0/28?

Network+ practice test questions, flashcards, and also mini-tutorials currently available.

## Looking in ~ a Classful Range

Consider a classful IP variety of 192.168.1.0/24. It supports 254 usable IP addresses in the selection of 192.168.1.1 through 192.168.1.254.

Note that two IP addresses cannot be assigned to any kind of host:

192.168.1.0 is the network ID.192.168.1.255 is the transfer address for the network.

## Using the Formula to recognize How plenty of Hosts

The formula for determining the number of hosts a network supports is 2n-2, whereby n is the number of bits provided for the host.

2n-2 is sometimes expressed as (2^n) – 2. Both indicate 2 raised to the power of n.You subtract two to reserve one IP because that the network ID and one because that the broadcast address.

Consider the classful IP selection of 192.168.1.0/24. The /24 is Classless Inter-Domain Routing (CIDR) notation indicating that 24 bits are offered for the subnet mask. One IPv4 resolve includes a full of 32 bits. With 24 bits provided for the subnet mask, that pipeline 8 bits for the master (32-24).

If girlfriend plug 8 right into the formula, it is (2^8) – 2. 2^8 is 256 and 256 – 2 is 254.

## Using a Calculator

Most calculators include a power formula, often provided as xy. The adhering to graphic shows the windows 10 built-in calculator in clinical mode.

To calculation (2^8) – 2, press the tricks in the complying with sequence.

2xy8–2

## Calculating hosts in Subnets

The preceding sections concentrated on a classful selection of IP addresses. However, you can use the same formula to identify how countless hosts a subnet supports. For example, how plenty of hosts can you to the right on this network: 192.168.1.0/28?

Remember that the formula for determining the variety of hosts a network supports is 2n-2, wherein n is the variety of bits offered for the host. The /28 is CIDR notation indicating the 28 bits are supplied for the subnet mask. An IPv4 resolve includes a total of 32 bits. Through 28 bits provided for the subnet mask, that leaves 4 bits for the hosts (32-28).

If girlfriend plug 4 into the formula, the is 2^4 – 2. 2^4 is 16 and 16 – 2 is 14.

2n-2 is periodically expressed as 2^n – 2. Both indicate 2 increased to the strength of n.You subtract two to to make reservation one IP because that the network ID and also one for the transfer address.

You deserve to use this method for any type of IP address with a CIDR notation that /25 or greater.

## Can You use a Calculator to recognize How countless Hosts?

You cannot take it a calculator into the test room. However, some exams provide access to a an easy calculator. Some don’t.

With this in mind, friend should have the ability to recreate the complying with table indigenous memory. This guarantee you have the right to identify the worth of 2n-2

CIDR# that Bits for HostsMax Hosts 2n-2
/24 8 254
/25 7 126
/26 6 62
/27 5 30
/28 414
/29 36
/30 2 2

## How plenty of Hosts Answer

Bart is designing a network segment the only requirements 24 IP addresses assigned. He needs to conserve the IP attend to space. What CIDR notation is the BEST an option for this network?

A. /25

B. /26

C. /27

D. /28

Answer: C is correct. The /27 Classless Inter-Domain Routing (CIDR) notation is the ideal choice. It shows a subnet mask that 255.255.255.224, which support 30 IP addresses and is the best choice to conserve IP resolve space.

The formula to determine how many hosts can operate top top a network is 2n-2, wherein n is the variety of 0 bits in the subnet mask.

A subnet mask has 32 bits. If the CIDR notation is /27 it indicates that there room 5 bits left to develop subnets. Utilizing the 2n-2 formula, or 25 – 2, or 32 – 2, you check out the price is 30. This is how countless hosts you deserve to have top top the network.

A is incorrect. A /25 CIDR notation shows 7 bits are left for hosts (32 – 25 = 7). Making use of the 2n-2 formula, or 27 – 2, or 128 – 2, you see the price is 126. In other words, /25 support 126 hosts. This is much much more than the 24 needed and also wastes IP addresses.

B is incorrect. A /26 CIDR notation indicates 6 bits room left because that hosts (32 – 26 = 6). Utilizing the 2n-2 formula, or 26 – 2, or 64 – 2, you check out the answer is 62. In other words, /26 support 62 hosts. This is much more than the 24 needed and also wastes IP addresses.

See more: Nutrition In Living Organisms Need Nutrients In Order To, Do All Living Organisms Need Nutrients

D is incorrect. A /28 CIDR notation shows 4 bits space left for hosts (32 – 28 = 4). Making use of the 2n-2 formula, or 24 – 2, or 16 – 2, you check out the price is 14. In other words, /28 supports 14 hosts, i m sorry isn’t sufficient to fulfill the need of 24 addresses in the question.