General problems with checksums (txcsum/rxcsum) on FreeBSD 8.0?

[Chuck Swiger]

Hi--

On Jan 15, 2010, at 11:12 AM, alan bryan wrote:
[ ... ]
> I'm currently sifting through a tcpdump in wireshark and there are all sorts of messages in there about checksums being incorrect - both TCP and UDP.

If you run tcpdump on a machine, it normally will receive the traffic being sent from that machine before the checksums are computed, especially if HW checksumming is being used.  For reliable detection of these problems, you need to look at the traffic either on a hub or via the monitoring or span port of a smart switch, although simply glancing at the checksum stats from "netstat -s" on both sides should indicate whether significant error rates are happening.

Regards,
-- 
-Chuck