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Zorluk: OrtaIPv4 Addressing and Subnetting

A network engineer is provisioning a dedicated VLAN for an isolated building management network that requires static IP address assignments for exactly 27 environmental control sensors. To conserve IPv4 address space while accommodating all devices, which subnet mask should be configured on the network interface?

  1. 255.255.255.224Cevap
  2. B
    255.255.255.240
  3. C
    255.255.255.192
  4. D
    255.255.255.248

Cevap

The subnet mask 255.255.255.224 (/27) is the correct choice as it provides 30 usable IP addresses, meeting the 27-host requirement with minimal address waste.
To support 27 host devices, the smallest block size needed must yield at least 27 usable IPs. Using 5 host bits gives 2^5 - 2 = 30 usable host IP addresses, which corresponds to a /27 prefix length or 255.255.255.224. This satisfies the requirement while minimizing address waste.

Adım Adım Çözüm

1
Determine the required number of usable host IP addresses.
The network requires at least 27 usable host IP addresses.
Each sensor requires a unique static IP address on the subnet.
2
Calculate the host bit requirement using the formula 2^h - 2 >= required_hosts.
For h = 5, 2^5 - 2 = 30 usable hosts (since 2^4 - 2 = 14 is too small).
Two addresses in every IPv4 subnet are reserved for the network ID and broadcast address.
3
Convert the host bits to a CIDR prefix and dotted-decimal subnet mask.
32 total bits - 5 host bits = /27 prefix. In dotted-decimal notation, /27 corresponds to 255.255.255.224.
The fourth octet has 3 network bits enabled (128 + 64 + 32 = 224).

Anahtar Kavram

Subnet Host Capacity and Mask Calculation
Tahmini Süre:1m 15s
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Konular

IPv4 Addressing and Subnetting

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