Hi, I captured all the packets from my computer for Ethernet card. I noticed for all the packets with source IP as my ethernet card IP got Header checksum error. I tried disabling the Checksum offload on my NIC. Also tried updating the NIC driver. Even on Wireshark the TCP prefernce is disabled for "Validate TCP checksum if possible". Still getting the capture with incorrect header checksum even for ICMP and all other traffic from my Ethernet IP. Also tried capturing using Ethereal. Got the same bad checksum. Please help me to identify the problem.. Is it with my NIC or where I have to check the .. What could be the problem. Regards, Sarav This question is marked "community wiki". asked 14 Apr '11, 04:23  Sarav |
One Answer:
Did you also disable "Validate the IP checksum if possible"? answered 14 Apr '11, 06:18  joke |
(What this means is that your adapter is probably doing IP and TCP checksum offloading, so that the IP and TCP implementations aren't computing the checksums and inserting them into the packet before handing them to the adapter - or to the capture mechanism and thus to tcpdump/Ethereal/Wireshark/etc. - so the application capturing the traffic sees packets with bad checksums. You need to turn off checksum validation to suppress the complaints.)