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Difficulty: MediumIPv4 Addressing and Subnetting

A network engineer is allocated the IPv4 address block 10.200.0.0/1910.200.0.0/19 to provision dedicated subnets for IP surveillance cameras across multiple industrial facilities. Each facility subnet must be configured using a 255.255.255.192255.255.255.192 subnet mask. How many distinct subnets can be created from this block?

Answer: 128 subnets

Answer

128 subnets can be created.
To determine the number of subnets created, convert the subnet mask 255.255.255.192255.255.255.192 to /26/26 CIDR notation. Borrowing bits from the original /19/19 prefix yields 26−19=726 - 19 = 7 subnet bits. Calculating 272^7 gives exactly 128 subnets.

Step-by-Step Solution

1
Determine the prefix length corresponding to the given subnet mask.
The dotted-decimal subnet mask 255.255.255.192255.255.255.192 corresponds to a /26/26 prefix (2424 network bits + 22 subnet bits in the fourth octet).
Converting the dotted-decimal mask to CIDR notation establishes the target prefix length.
2
Calculate the number of borrowed subnet bits.
26 bits (new prefix)−19 bits (original prefix)=7 borrowed subnet bits26 \text{ bits (new prefix)} - 19 \text{ bits (original prefix)} = 7 \text{ borrowed subnet bits}.
Subnetting extends the network prefix length from /19/19 to /26/26.
3
Compute the total number of subnets.
27=1282^7 = 128 total subnets.
The formula to calculate the number of subnets generated by borrowing ss bits is 2s2^s.

Key Concept

Subnet Count Calculation
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Topics

IPv4 Addressing and Subnetting

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