Of which of the following ICMP replies are there two versions, which are: the standard version that simply states the packet had the Don't Fragment bit set when it reached a router that needed to fragment it, and the PMTU version that includes information about the restricting link?
A)Code 2: Protocol Unreachable
B)Code 3: Port Unreachable
C)Code 4: Fragmentation Needed and Don't Fragment Was Set
D)Code 5: Source Route Failed

Question

Quizplus · Accepted Answer

Code 4: Fragmentation Needed and Don't Fragment Was Set is the ICMP message that has two versions: the standard version and the PMTU (Path MTU Discovery) version. The standard version indicates that a packet with the Don't Fragment bit set could not be fragmented, and the PMTU version includes information about the maximum transmission unit (MTU) size that the packet can be transmitted without fragmentation.

Of Which of the Following ICMP Replies Are There Two