Hello Iliri,
the reason that you see a packet loss in your ping results with packets of a datagram size of 2000 is that the end-to-end path acn only handle packets smaller than that packet size. Therefore, the packets have to be fragmented, which can cause delays. The default timeout on a Cisco router is 2 seconds, which means that when the delay is larger than those two seconds, you will see a '.' instead of a '!'. This does not necessarily mean that the packet is not transmitted at all, it just means that there is no reply within those two seconds. Try and extended ping and set the timeout to something higher than 2 seconds...
HTH,
GNT
