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Every time I open my browser, I get tons of these bad header reports. What does this stem from?

Wireshark Readout

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Probably because, as Wireshark notes on the first red line in the display, your OS and network adapter are doing IP checksum offloading, and the packets in question are being sent by your machine, so that the CPU sends them to the network adapter with the IP checksum set to 0, and the network adapter computes the checksum and fills it in before sending the packet.

As the mechanisms used by libpcap/WinPcap to capture packets sees transmitted packets before they are handed to the network adapter (the only way for to see them after they're handed to the network adapter is to attach a separate network adapter to the network and capture them after they've been transmitted on the network), they will see packets with an IP checksum of 0.

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This seems like the correct answer, but I cannot be sure... – JVE999 Nov 11 '13 at 23:43

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