Subnetting involves borrowing bits from the host portion to create smaller networks.

• A. Subnetting
• B. Supernetting
• C. VLSM
• D. NAT

Answer: (A)

Subnetting is the process of creating smaller networks from a larger one by extending the network prefix. When you borrow bits from the host portion of an IP address, you move those bits into the network portion through the subnet mask. Each bit you borrow increases the number of subnets (doubling it with each bit) but reduces the number of usable host addresses in each subnet, because more bits are now used to identify subnets rather than hosts.

For example, starting with a typical Class C network (24 bits for the network, 8 for hosts), borrowing 3 bits from the host portion gives a new mask of 255.255.255.224. This creates 8 subnets, each with up to 30 usable hosts. This illustrates the trade-off: more subnets with fewer hosts per subnet.

Supernetting, on the other hand, combines adjacent networks to form a larger one by using fewer network bits. NAT translates private addresses to public ones for Internet access, which is a different concept from subnetting. VLSM (Variable Length Subnet Masking) is a subnetting technique that allows subnets to have different masks, providing flexibility with address allocation while still borrowing bits from the host portion.