Maximum Possible Subnets with CIDR Block 10.0.1.0/27

Answer - B.

In AWS, a VPC is limited to /28 CIDR range to the maximum number of subnets is actually 2.

Ex: 1 x /27 CIDR can be split into 2 x /28 subnets.

The CIDR block of 10.0.1.0/27 represents a block of IPv4 addresses that consists of 32 bits, with the first 27 bits representing the network part and the remaining 5 bits representing the host part. The formula for calculating the number of subnets in a given CIDR block is 2^(subnet bits).

In this case, the CIDR block has 27 subnet bits, which means that the number of possible subnets is 2^(27) = 134217728.

However, there is a caveat to keep in mind when designing subnets in AWS. AWS reserves five IP addresses in each subnet for its own use. These include the first four IP addresses (network, router, DNS server, and future use) and the last IP address (broadcast). Therefore, the maximum number of usable IP addresses in each subnet is 2^(5) - 5 = 27.

Using this information, we can calculate the maximum number of subnets possible with the given CIDR block as follows:

• Total number of IP addresses in the CIDR block = 2^(32-27) = 2^(5) = 32
• Number of usable IP addresses in each subnet = 2^(5) - 5 = 27
• Maximum number of subnets = total number of IP addresses / usable IP addresses = 32 / 27 = 1.185 (rounded down to 1)

Therefore, the correct answer is A. 1 * 27.