bad tcp cksum on outgoing packets

Chris Stenton jacs at
Thu Aug 12 05:02:17 PDT 2004

I have just been doing some debugging on my 5.2.1 box and noticed that
outgoing tcp packets on the box are coming up with bad checksums on
tcpdump. I am using the nge interface.

Here is a sample output.

12:44:29.458021 0:4:e2:10:60:83 0:c:6e:4e:a0:cc ip 82: > P [bad tcp cksum 9420!]
2071:2099(28) ack 753 win 65535 (DF) [tos 0x10]  (ttl 64, id 35623, len
68, bad cksum 0!)

12:44:29.642088 0:c:6e:4e:a0:cc 0:4:e2:10:60:83 ip 60: > . [tcp sum ok] 753:753(0)
ack 2099 win 64956 (DF) (ttl 128, id 44852, len 40)

Any ideas whats going on as the packet does not seem to be resent?


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