When an IP datagram is fragmented, the headers for all the fragmented datagrams will be essentially the same. The only fields in the header that will be changed is:
the total length because now the packets are smaller,
the more fragments field except for the last fragment which will not have a value in that field,
the fragment offset which shows the position the fragment has in relation to the original (now fragmented) datagram,
and the header checksum.
Things like source/destination, etc. will be retained in each fragment.
-Jeremy-
