Which statement best describes the relationship between MTU and fragmentation?

• A. Fragmentation never happens on IPv4.
• B. Fragmentation occurs at the end host only.
• C. Fragmentation occurs on every link regardless of MTU.
• D. If a packet size exceeds the MTU, routers will fragment the packet.

Answer: (D)

The main idea is that MTU sets the maximum datagram size a link can carry without breaking it up. When a device forwards a packet, it checks the MTU of the next link. If the packet is larger than that MTU, a router along the path can split the datagram into smaller fragments so each piece fits the link’s MTU. Those fragments travel onward and are reassembled at the destination (if possible). This explains why fragmentation isn’t confined to the end host and doesn’t happen on every link—only on links whose MTU is smaller than the packet, and only when fragmentation is permitted. Therefore, the statement that best describes the relationship is that if a packet size exceeds the MTU, routers will fragment the packet.