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Difficulty: MediumIPv4 Addressing and Subnetting

A network engineer is assigned the IPv4 subnetwork block 192.168.100.0/23192.168.100.0/23 for a high-density enterprise server rack. What is the maximum number of usable host IPv4 addresses that can be assigned to active network interfaces within this subnet?

Answer: 510 hosts

Answer

510 usable host addresses
A /23/23 prefix leaves 32−23=932 - 23 = 9 bits for host addresses. Total addresses equal 29=5122^9 = 512. Subtracting 2 for the network address (192.168.100.0192.168.100.0) and broadcast address (192.168.101.255192.168.101.255) leaves exactly 510 usable host IP addresses.

Step-by-Step Solution

1
Calculate the number of host bits from the prefix length.
Host bits = 32−23=932 - 23 = 9 bits
An IPv4 address consists of 32 bits. Subtracting the prefix length yields the remaining host portion bits.
2
Calculate the total number of IPv4 addresses in the subnetwork block.
29=5122^9 = 512 total addresses
The formula 2n2^n gives the complete block size in total IP addresses.
3
Subtract reserved subnetwork and broadcast addresses to determine usable host capacity.
512−2=510512 - 2 = 510 usable hosts
The lowest address in the subnet acts as the subnet ID, and the highest address acts as the directed broadcast address; neither can be assigned to host interfaces.

Key Concept

IPv4 Usable Host Calculation
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Topics

IPv4 Addressing and Subnetting

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