In IPv4, what allows fragmentation to occur if a packet is larger than the path MTU?

• A. The sender never fragments
• B. The destination host fragments
• C. Routers may fragment the packet
• D. Fragmentation is not allowed in IPv4

Answer: (C)

In IPv4, fragmentation happens when a packet is too large for the next hop’s maximum transmission unit (MTU). Routers along the path can split that large datagram into smaller fragments that fit the MTU of the outgoing link. Each fragment carries enough header information to allow the destination to reassemble the original datagram once all fragments arrive. This is why fragmentation is performed by routers as the packet moves toward its destination. If a router is not allowed to fragment (the Don't Fragment bit is set) and the packet exceeds the MTU, the router will drop it and send back an ICMP message instead.