Bad checksums ruining my day

  • Upon running a packet capture (from webGUI), I'm noticing that 5-10% of my packets have bad IP header checksums (getting 0x0000 instead of an actual checksum). I've checked the box in webGUI to disable checksum offloading; this didn't help, or perhaps made it all worse.

    Does anybody have any idea what may be wrong?

  • Check cables, check switches, check the NIC.

    If you can do this: try to sniff traffic between the switch and your pfSense directly to see if the problem is on the NIC in the pfSense box side or on the switch side.

  • Thanks for replying! I wish more people here were as helpful as you were. Yes, packet sniffing showed that the problem existed outside the NIC as well. It turns out that the Broadcom NetXtreme Gigabit NICs built into my Dell 2650 were both causing many (up to 35%) CRC errors, but the addon NICs were not. I simply don't use the embedded NICs anymore - problem solved.

    I wonder if this is a known issue with these controllers… I can't find any info.

    Thanks again!

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