Question

What are the assignable addresses for the 12th subnet with the network address of 220.100.100.0 and the number of needed subnets is 45? a. 220.100.100.42 to 220.100.100.51 b. 220.100.100.52 to 220.100.100.55 c. 220.100.100.45 to 220.100.100.46 d. 220.100.100.40 to 220.100.100

Answer 1

Answer:

C. 220.100.100.45 to 220.100.100.46

Explanation:

The Classless IP subnetting of 220.100.100.0 begins from the fourth octet of the IP address. To get 45 subnet mask, it uses 6 bits from the fourth octet, which approximately give 64 subnets, while the remaining 2 bits are used for host IP addressing.

The useable host IP addresses are gotten from the formula '$2^{n}$-2', with n=2 bits.

useable host IP addresses = 2^2 - 2 = 2 addresses per subnet.

While the 12th subnet is 12 x 2^2 = 44.

This means that the 12th subnet mask starts with 220.100.100.44 (as the network address) and ends with 220.100.100.47 as broadcast IP address, while '.45' and '.46' are the assignable addresses of the subnet.