DUPLICATE AND DAMAGED PACKETS
The ping utility will report duplicate and damaged packets. Duplicate
packets should never occur when pinging a unicast address, and seem to be
caused by inappropriate link-level retransmissions. Duplicates may occur
in many situations and are rarely (if ever) a good sign, although the
presence of low levels of duplicates may not always be cause for alarm.
[B]Duplicates are expected when pinging a broadcast or multicast address,
since they are not really duplicates but replies from different hosts to
the same request.[/B]
Damaged packets are obviously serious cause for alarm and often indicate
broken hardware somewhere in the ping packet's path (in the network or in
the hosts).