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Zorluk: ZorIPv4 Addressing and Subnetting

A network engineer is configuring an internal routing domain using the assigned IP address block 10.88.0.0/1810.88.0.0/18. The network architecture requires dividing this entire /18/18 block into equal-sized subnets such that each subnet can accommodate at least 180180 usable host IP addresses while maximizing the number of subnets created. How many total subnets can be created from the original block using this optimal subnet mask?

Cevap: 64 subnets

Cevap

64 subnets can be created from the original block.
To support at least 180 usable hosts per subnet, each subnet requires 8 host bits because 28−2=2542^8 - 2 = 254 usable IP addresses (27−2=1262^7 - 2 = 126 is insufficient). An 8-host-bit subnet corresponds to a /24/24 prefix (32−8=2432 - 8 = 24). Dividing a /18/18 network block into /24/24 subnets yields 224−18=26=642^{24 - 18} = 2^6 = 64 equal-sized subnets.

Adım Adım Çözüm

1
Calculate the minimum number of host bits required per subnet
8 host bits (h=8h = 8)
Usable hosts formula is 2h−22^h - 2. For 180180 hosts, 2h−2≥180  ⟹  2h≥1822^h - 2 \ge 180 \implies 2^h \ge 182. Since 27=1282^7 = 128 is insufficient, 28=2562^8 = 256 is required, providing 254254 usable host IP addresses.
2
Determine the optimal CIDR subnet mask prefix length
/24 prefix length (255.255.255.0255.255.255.0)
Subtracting the 88 required host bits from 3232 total IPv4 address bits yields 32−8=2432 - 8 = 24 network/subnet bits.
3
Calculate the total number of subnets derived from the original /18 block
64 subnets
The number of borrowed subnet bits is 24−18=624 - 18 = 6 bits. The total number of available subnets is 26=642^6 = 64.

Anahtar Kavram

Equal-length IPv4 Subnetting and Host Requirement Calculation
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Konular

IPv4 Addressing and Subnetting

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