IPv4 subnets are created by borrowing bits from the host portion of the IP address.

• A. Sometimes
• B. True
• C. False
• D. Not Applicable

Answer: (B)

Subnets come from changing how the address is divided between network and host bits. The subnet mask shows which bits are part of the network. To create more networks within a given range, you take some of the bits that used to be host bits and treat them as network bits instead—this is borrowing bits from the host portion. By doing this, you extend the network prefix and get more subnets, at the cost of fewer host addresses per subnet. For example, moving from a /24 to a /25 splits one network into two subnets, each with 128 addresses. This is the standard way IPv4 subnetting works, so the statement is true. The other options aren’t accurate because subnetting is defined by borrowing host bits to form subnets, not by any circumstance where it wouldn’t apply or where it’s irrelevant.