Check capture offloading before diagnosing checksum corruption

Determine where packets were captured before treating invalid outbound checksums as a network fault.

Source facts

Wireshark explains that a capture can see locally generated outgoing packets before network hardware finishes checksum offloading. Such packets can appear to have invalid checksums in the capture even though the transmitted packets are valid. This explanation applies to packets generated at the capture point, not automatically to received traffic. The guide also notes that enabled checksum validation can affect packet reassembly when a checksum is considered invalid.

Source: Wireshark — User’s Guide, Checksums.

Applicability

Use this when investigating checksum warnings in a host capture. Record traffic direction, capture location, adapter settings, and Wireshark validation preferences before drawing a conclusion.

DSE recommendation

DSE recommends preserving the original capture and comparing the same approved flow from another suitable observation point. Correlate the warning with actual connection symptoms, retransmissions, and application results. Distinguish a capture artifact from a measured on-wire error before replacing equipment or changing drivers. Keep any temporary offload change within a controlled test and restore the accepted configuration afterward. Limit captures to the authorized diagnostic scope and handle packet contents according to the organization’s data policy.

Verification

Compare outbound and received packets and the corresponding peer-side observation where available. Record whether the warning persists beyond the originating host. Retain the capture method and relevant preferences with the finding so another reviewer can understand why a warning was accepted or escalated.

Official reference

Wireshark — User’s Guide, Checksums. Reviewed October 14, 2026.