Hi Farooq,
When you send packets larger than the path mtu, these packets need to be fragmented. The fragmented packets then need to be reassembled by the destination host. The fact that ping packets are being dropped might have to do with the destination host not being able to properly reassemble all the packets. If you are trying to test the capacity of the circuit, I would suggest better tools such as iperf.
Regards
Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
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