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Zorluk: OrtaIPv4 Addressing and Subnetting

A network administrator is provisioning a dedicated management VLAN to connect 14 top-of-rack switch interfaces and 1 central default gateway interface. To minimize wasted IP address space, which of the following CIDR prefix lengths represents the smallest subnet mask that can accommodate all 15 required interfaces?

  1. /2727Cevap
  2. B
    /2828
  3. C
    /2626
  4. D
    /2929

Cevap

The prefix length /2727 is the smallest subnet that provides enough usable IP addresses for 15 host interfaces.
The prefix length /2727 allocates 5 host bits (32−27=532 - 27 = 5), providing 25−2=302^5 - 2 = 30 usable IP addresses. This is the smallest valid subnet mask that accommodates all 15 required host interfaces (14 switches + 1 default gateway).

Adım Adım Çözüm

1
Determine the total number of required usable host IP addresses.
14 switch interfaces + 1 default gateway interface = 15 usable IP addresses required.
Every active device interface on the subnet requires a unique usable IPv4 address.
2
Calculate usable host capacity using the IPv4 host capacity formula (2n−22^n - 2).
For n=4n=4 host bits (/2828), capacity is 24−2=142^4 - 2 = 14 usable hosts. For n=5n=5 host bits (/2727), capacity is 25−2=302^5 - 2 = 30 usable hosts.
Two IP addresses in every IPv4 subnet are reserved for the network ID and broadcast address and cannot be assigned to hosts.
3
Select the smallest prefix length that meets or exceeds the required 15 hosts.
The prefix length /2727 provides 30 usable host IP addresses, satisfying the 15 host requirement with minimal address waste.
A /2828 subnet only provides 14 usable addresses, falling short by 1 IP address.

Anahtar Kavram

IPv4 Subnet Mask Selection and Usable Host Calculation
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Konular

IPv4 Addressing and Subnetting

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