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Difficulty: EasyIPv4 Addressing and Subnetting

A network administrator is configuring a local network segment using the prefix /24/24 (subnet mask 255.255.255.0255.255.255.0). What is the maximum number of usable host IPv4 addresses that can be assigned to devices on this subnet?

  1. 254254Answer
  2. B
    256256
  3. C
    255255
  4. D
    128128

Answer

The maximum number of usable host IPv4 addresses on a /24/24 subnet is 254254.
For any standard IPv4 subnet, the formula to calculate usable host addresses is 2n−22^n - 2, where nn represents the number of host bits. A /24/24 CIDR prefix leaves 88 host bits (32−24=832 - 24 = 8). Calculating 282^8 yields 256256 total IP addresses. Subtracting 22 (one for the subnet network identifier and one for the subnet broadcast address) leaves exactly 254254 usable host addresses.

Step-by-Step Solution

1
Calculate the number of host bits in the prefix.
32−24=832 - 24 = 8 host bits.
An IPv4 address consists of 32 bits in total.
2
Calculate the total number of IP addresses in the subnet.
28=2562^8 = 256 total addresses.
The total address capacity of a subnet is 2n2^n, where nn is the number of host bits.
3
Subtract reserved IP addresses to find the usable host count.
256−2=254256 - 2 = 254 usable host addresses.
The network address (all host bits 0) and the broadcast address (all host bits 1) cannot be assigned to network host interfaces.

Key Concept

Subnet Usable Host Count Calculation
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Topics

IPv4 Addressing and Subnetting

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