The number of bits borrowed to create subnets is indicated by the ______.

• A. Subnet Mask
• B. IP Address
• C. Default gateway
• D. DNS Server

Answer: (A)

Bits borrowed to create subnets come from the host portion of the address, and the subnet mask shows how many bits are used for the network/subnet portion. The mask is made of ones where the network (including subnets) bits live and zeros for the remaining host bits; counting the leading ones tells you how many bits are designated for the network, which increases as you borrow more bits for subnets. In CIDR terms, this is expressed as the prefix length. For example, a mask like 255.255.255.192 corresponds to a /26, meaning two bits have been borrowed from the host part to create subnets. The mask thus indicates exactly how many bits are used for subnetting. Other options describe different things: an IP address identifies a specific device, a default gateway is the router’s address on the local network, and a DNS server resolves names to IPs, none of which tell you how many subnet bits were borrowed.