pls check:http://groups.google.com/group/comp.os.linux.networking/browse_thread/thread/e78dcec56b41fbf9/e592a9bc2441c430?lnk=st&q=NO+FLAGS+are+set%2C40+headers+%2B+0+data+bytes&rnum=6#e592a9bc2441c430
# hping2 -c 1 -y -d 1500 -m 10000 megahard eth0 default routing interface selected (according to /proc) HPING megahard (eth0 192.168.1.1): NO FLAGS are set, 40 headers + 1500 data bytes [send_ip] sendto: Message too long
This packet required a MTU of 1540 bytes, DF (don't fragment) was set and the packet could not be sent.
Let's try again:
# hping2 -c 1 -y -d 1460 -m 10000 megahard eth0 default routing interface selected (according to /proc) HPING megahard (eth0 192.168.1.1): NO FLAGS are set, 40 headers + 1460 data bytes 46 bytes from 192.168.1.1: flags=RA seq=0 ttl=255 id=8562 win=0 rtt=2.8 ms
--- megahard hping statistic --- 1 packets tramitted, 1 packets received, 0% packet loss round-trip min/avg/max = 2.8/2.8/2.8 ms
This time it worked, proving that a MTU of 1500 does not require fragmentation.
Repeat above with your ISP's gateway and vary the ``-d nnnn'' until you discover the optimum MTU. [b]Sample Text
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