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Difficulty: MediumIPv4 Addressing and Subnetting

A network engineer is configuring a newly provisioned server rack in a data center using the assigned IPv4 subnet block 10.50.16.0/2710.50.16.0/27. What is the maximum number of usable host IPv4 addresses that can be assigned to active devices within this subnet block?

Answer: 30 addresses

Answer

The maximum number of usable host IPv4 addresses in a /27 subnet is 30.
A CIDR prefix of /27 leaves 5 host bits (32−27=532 - 27 = 5). Raising 2 to the power of 5 gives 32 total addresses. Subtracting the network address and broadcast address (32−232 - 2) results in 30 usable host IP addresses.

Step-by-Step Solution

1
Determine the number of available host bits.
Host bits = 32−27=532 - 27 = 5 bits.
An IPv4 address has 32 bits total. Subtracting the prefix length yields the bits remaining for host addressing.
2
Calculate the total size of the address block.
Total IP addresses = 25=322^5 = 32 addresses.
Five host bits allow 252^5 distinct binary combinations.
3
Subtract reserved addresses to find the usable host count.
Usable host addresses = 32−2=3032 - 2 = 30 addresses.
The network address (all host bits 0) and the directed broadcast address (all host bits 1) cannot be assigned to network hosts.

Key Concept

Usable Host Calculation in Subnetting
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Topics

IPv4 Addressing and Subnetting

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