The number of fragments

What this IPv4 fragmentation interview question tests

This is a medium-difficulty networking question that tests your understanding of how routers handle packets that exceed the maximum transmission unit (MTU) of an outgoing link. It is commonly asked at firms building trading infrastructure, market-data systems, or any platform where network reliability and latency matter.

To solve problems like this, you need to understand the IPv4 fragmentation rules: how the payload is divided, what overhead is added by the IP header, and how the fragment offset field constrains the size of each fragment. The question rewards careful attention to the specification and correct arithmetic, not guesswork.

• IPv4 header structure and minimum size
• Fragment offset field and alignment constraints
• Payload vs. total packet size calculations
• How routers decide whether and how to fragment