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Zorluk: ZorIPv4 Addressing and Subnetting

A network administrator is allocated the IPv4 address block 172.20.64.0/21172.20.64.0/21 for datacenter VLAN expansion. The architectural requirement mandates that the block be divided into the maximum possible number of equal-sized subnets such that each subnet can accommodate at least 5050 usable host addresses. If exactly 5050 hosts are assigned in every created subnet, how many usable host IP addresses across the entire /21/21 block remain unassigned?

Cevap: 384 addresses

Cevap

384 usable host IP addresses remain unassigned across all created subnets.
To satisfy the requirement of at least 5050 usable host addresses per subnet while maximizing the number of subnets, 66 host bits are required (26−2=622^6 - 2 = 62 usable host addresses per subnet), resulting in a /26/26 prefix length. Dividing the /21/21 block into /26/26 subnets produces 226−21=322^{26-21} = 32 subnets. With 5050 host addresses assigned per subnet, each subnet has 62−50=1262 - 50 = 12 unassigned usable host addresses. Across all 3232 subnets, the total number of unassigned usable host IP addresses is 32×12=38432 \times 12 = 384.

Adım Adım Çözüm

1
Determine the minimum host bits required to support at least 50 usable host addresses per subnet.
6 host bits (h=6h = 6), which yields 26−2=622^6 - 2 = 62 usable host addresses per subnet and a prefix length of /26/26.
Using 5 host bits (25−2=302^5 - 2 = 30) is insufficient for 50 hosts. 6 host bits meet the minimum requirement while maximizing subnet creation.
2
Calculate the total number of /26/26 subnets created from the /21/21 summary block.
226−21=25=322^{26 - 21} = 2^5 = 32 subnets.
Borrowing 5 subnet bits from a /21/21 block creates 32 subnets of size /26/26.
3
Determine the unassigned usable host addresses per subnet when 50 hosts are assigned.
62−50=1262 - 50 = 12 unassigned usable host addresses per subnet.
Network and broadcast addresses are already excluded when calculating the 62 usable host addresses.
4
Multiply the unassigned usable host addresses per subnet by the total number of created subnets.
32 subnets×12 addresses=38432 \text{ subnets} \times 12 \text{ addresses} = 384 total unassigned usable host IP addresses.
Aggregating the unused host capacity across all equal-sized subnets within the allocated block.

Anahtar Kavram

IPv4 Subnet Sizing and Usable Host Capacity Calculation
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Konular

IPv4 Addressing and Subnetting

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