2011/6/6 mold2010 <[email protected]>: > The root cause of this problem is found. It is because the MTU of the > receiving NIC is set to 9000, which is greater than 1500. Since some packets > have ethernet FCS and trailer, that makes the packet has a 1520 whole size. > The tcpreplay can not recognize the FCS and trailer in the IP packet end, > they are treated as part of IP layer, so the 1520 bytes packets can not be > sent to the peer. I updated the sending side NIC MTU from 1500 to 9000 and > did the same to the receiving side NIC. But the hardware seems like do not > support MTU more than 1500. So this strange problem is seen. > After I changed the MTU back to 1500, everything works fine except the 1520 > bytes packets can not be sent successfully. I plan to make a tool to trim the > FCS and trailer, so the 1520 bytes will not be an issue. > An interesting thing is after I set the MTU to 9000 for receiving side, every > packet can be captured. Seems some kind mechanism of Linux is invoked, no > packets loss, just length cut. This is interesting.
I'm curious, have you tried tcprewrite's --efcs option? If it doesn't work, please open a ticket at http://tcpreplay.synfin.net and attach a sample pcap. -- Aaron Turner http://synfin.net/ Twitter: @synfinatic http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & Windows Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. -- Benjamin Franklin "carpe diem quam minimum credula postero" - This is the tcpdump-workers list. Visit https://cod.sandelman.ca/ to unsubscribe.
