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Question

Difficulty: EasyIPv4 Addressing and Subnetting

A network technician is configuring a new subnet with an IPv4 prefix length of /28/28. How many usable host IPv4 addresses are available on this subnet?

Answer: 14 addresses

Answer

14 usable IPv4 host addresses are available on a /28 subnet.
For a /28/28 prefix, the host portion contains 32−28=432 - 28 = 4 bits. The formula to calculate usable hosts is 2h−22^h - 2, where hh is the number of host bits. Therefore, 24−2=16−2=142^4 - 2 = 16 - 2 = 14 usable host IPv4 addresses.

Step-by-Step Solution

1
Determine the number of host bits available.
Host bits = 32−28=432 - 28 = 4 bits.
An IPv4 address consists of 32 bits. Subtracting the prefix length (/28) leaves the host portion of the address.
2
Calculate total IP address space for the subnet.
Total addresses = 24=162^4 = 16 addresses.
The formula 2h2^h determines total IP address combinations, where hh is the number of host bits.
3
Subtract reserved addresses to get usable host addresses.
Usable addresses = 16−2=1416 - 2 = 14 addresses.
The first address (subnet ID) and last address (broadcast) cannot be assigned to individual hosts.

Key Concept

IPv4 Subnet Usable Host Calculation
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Topics

IPv4 Addressing and Subnetting

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