Why in tcpdump logs error like 'bad udp cksum' is seen ?

Solution Verified - Updated -

Issue

  • Running tcpdump like below produces error , bad udp cksum:
# tcpdump -nvv -i bond0 multicast and port 18113

tcpdump: listening on bond0, link-type EN10MB (Ethernet), capture size 96 bytes
20:16:59.109023 IP (tos 0x0, ttl   1, id 0, offset 0, flags [DF], proto: UDP (17), length: 61) nn.nn.nn.nn.18113 > nn.nn.nn.nn.18113: [bad udp cksum 3965!] UDP, length 33

Environment

  • Red Hat Enterprise Linux (Any Version)
  • Network Interface Cards which support offloading
  • tcpdump

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