CCNA 200-125 Exam: Valid Host Addresses with Subnet Mask

Valid Host Addresses

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Assuming a subnet mask of, three of the following addresses are valid host addresses.

Which are these addresses? (Choose three.)



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A. B. C. D.


To determine which of the given IP addresses are valid host addresses with the subnet mask of, we first need to understand how subnet masks work. A subnet mask is a 32-bit value that is used to divide an IP address into two parts: the network portion and the host portion. The subnet mask has 1's in the network portion and 0's in the host portion.

In this case, the subnet mask of has the following binary representation:

11111111 11111111 11111000 00000000

This means that the first 21 bits of an IP address are used to represent the network portion, while the remaining 11 bits are used to represent the host portion.

To determine the valid host addresses for a given network, we need to identify the range of IP addresses that can be used for hosts within that network. The first and last addresses in the range are reserved for the network address and the broadcast address, respectively, so we cannot use those addresses for hosts.

To calculate the valid range of IP addresses, we need to determine the network address for the given subnet and then add 1 to get the first valid host address. We also need to determine the broadcast address for the subnet and subtract 1 to get the last valid host address.

To calculate the network address, we perform a logical AND operation