Subnetting 172.17.32.0/23 to /27: Number of Subnets and Usable Host Addresses

# How many subnets can be gained by subnetting 172.17.32.0/23 into a /27 mask, and how many usable host addresses will there be per subnet?

### Question

How many subnets can be gained by subnetting 172.17.32.0/23 into a /27 mask, and how many usable host addresses will there be per subnet?

### Explanations

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A. B. C. D. E.

C

Subnetting from /23 to /27 gives us 27 23 = 4 bits -&gt; 24 = 16 subnets.

/27 has 5 bit 0s so it gives 25 2 = 30 hosts-per-subnet.

To answer this question, we need to understand some basics of subnetting and IP addressing.

Subnetting is the process of dividing a network into smaller subnetworks (subnets) to increase network efficiency and flexibility. An IP address is a unique identifier that is assigned to devices on a network. IPv4 addresses are 32-bit addresses represented in dotted decimal notation, such as 172.17.32.0.

The subnet mask is a 32-bit value used to divide an IP address into network and host portions. The subnet mask consists of a series of 1's followed by a series of 0's. In this case, the original subnet mask is /23, which means the first 23 bits of the 32-bit IP address represent the network portion, leaving the last 9 bits for the host portion.

To subnet the network 172.17.32.0/23 into /27 subnets, we need to borrow 4 bits from the host portion of the IP address. This leaves 5 bits for the host portion of the IP address, which means that each subnet can have 2^5 (32) possible host addresses.

The new subnet mask for the /27 subnets will be 255.255.255.224. This means that the first 27 bits of the 32-bit IP address represent the network portion, leaving the last 5 bits for the host portion.

To calculate the number of subnets, we need to determine how many times we can divide the original network into smaller /27 subnets. To do this, we need to calculate the number of bits we borrowed from the host portion of the IP address (4 bits) and raise 2 to that power (2^4 = 16). This means that we can create 16 subnets.

To calculate the number of usable host addresses per subnet, we subtract 2 from the total number of possible host addresses (32) to account for the network address and broadcast address, which cannot be used for host addresses. This leaves us with 30 usable host addresses per subnet.

Therefore, the correct answer is C. 16 subnets, 30 hosts.