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Zorluk: OrtaIPv4 Addressing and Subnetting

A network administrator is designing an IP addressing scheme for a newly provisioned server VLAN. The VLAN must accommodate static IPv4 address assignments for 30 application servers, 1 default gateway router interface, and 1 monitoring appliance (a total of 32 usable host IP addresses). Which of the following represents the smallest CIDR prefix that satisfies this requirement?

  1. /26Cevap
  2. B
    /27
  3. C
    /28
  4. D
    /25

Cevap

The correct subnet mask is /26 because it provides 62 usable host IP addresses, which is the smallest CIDR prefix capable of accommodating all 32 required host devices.
To host 32 devices, a subnet must supply at least 32 usable IP addresses. Because 2 addresses are reserved for network and broadcast identification (2h−22^h - 2), 5 host bits (/27) only provide 30 usable addresses. Therefore, 6 host bits (/26) are required, offering 62 usable host IP addresses, making it the smallest prefix that meets the 32-device requirement.

Adım Adım Çözüm

1
Calculate the total number of usable host IP addresses required.
30 application servers + 1 default gateway + 1 monitoring appliance = 32 usable host IP addresses.
Every network-attached interface requires a unique usable IPv4 host address.
2
Apply the usable host formula 2h−2≥required hosts2^h - 2 \ge \text{required hosts} to find the necessary host bits (hh).
Testing h=5h = 5: 25−2=302^5 - 2 = 30 usable hosts (insufficient). Testing h=6h = 6: 26−2=622^6 - 2 = 62 usable hosts (sufficient).
Two IP addresses in every subnet are reserved for the network ID (all host bits 0) and the broadcast address (all host bits 1).
3
Calculate the CIDR prefix from the required host bits.
32 total IPv4 bits - 6 host bits = /26 subnet prefix.
The CIDR prefix notation represents the number of network bits (32−h32 - h).

Anahtar Kavram

IPv4 Subnet Mask Calculation and Reserved Addresses
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Konular

IPv4 Addressing and Subnetting

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