How is the network address obtained when performing a bitwise AND operation between an IP address and a subnet mask?

• A. The network address is obtained by bitwise ANDing the IP address with the subnet mask.
• B. The network address is obtained by bitwise ORing the IP address with the subnet mask.
• C. The network address is obtained by bitwise XORing the IP address with the subnet mask.
• D. The network address is simply the IP address masked by the host bits.

Answer: (D)

To find the network address, you use the subnet mask to separate the network portion from the host portion. The operation is a bitwise AND between the IP address and the subnet mask. Each bit is kept if the mask has a 1 there (network part) and cleared to 0 if the mask has a 0 there (host part). This zeros out the host bits and leaves the network bits intact, giving the network address.

For example, with IP 192.168.10.77 and a 255.255.255.0 mask, the result is 192.168.10.0. That shows the network portion defined by the mask.

Other operations aren’t used to derive the network address: OR would set more bits to 1, XOR would flip bits, and simply taking the IP address ignores the boundary defined by the mask.