IP header corruption occurs when which elements are swapped exactly in the IP header?

• A. 16-bit fields swapped within 8-bit boundaries
• B. 16-bit fields swapped exactly in the IP header
• C. Two 8-bit fields swapped
• D. Source and destination addresses overwritten

Answer: (B)

Swapping 16-bit fields exactly in the IP header means exchanging whole 16-bit words between positions, while keeping each field’s size and boundary intact. The IP header is a fixed layout where each 16-bit word corresponds to specific fields (like Total Length, Identification, Flags/Fragment Offset, and the Header Checksum). If you swap these 16-bit words, each field ends up with the value of the one it swapped with, which corrupts the meaning of multiple fields at once. The packet would be misinterpreted: the reported length might not match the actual data, fragmentation information could be wrong, and the header checksum would no longer be valid. This exact type of swap directly disrupts the header’s integrity, making it a classic way to cause header corruption.

Swapping two 8-bit fields or overwriting source and destination addresses are different kinds of changes than this exact 16-bit-word swap, and they don’t describe the same precise mechanism tested here.