Question

A router receives an IP packet with source IP address 182.12.15.10. When the IP header is processed, it finds that the content of header HLEN field is 3. Identify the ICMP message generated by the router.

Answer 1

When the IP header is processed, it finds that the content of header HLEN field is 3.
Here, Header Length is changed.
Whenever packets come to the router then router will calculate header checksum.
And it will match the calculated checksum to recieved header checksum.But It will not match,because Header Length is changed.
Therefore, ICMP packet will generated.
ICMP will take the source IP from the discarded packet and informs to source by sending parameter problem message.