From owner-freebsd-net@FreeBSD.ORG  Wed Mar 17 17:30:35 2004
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Date: Wed, 17 Mar 2004 20:30:34 -0500
From: Barney Wolff <barney@databus.com>
To: Sherwood Botsford <sbotsford@sjsa.ab.ca>
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Subject: Re: tcpdump says errors.  Netstat says no.
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On Wed, Mar 17, 2004 at 07:38:11AM -0700, Sherwood Botsford wrote:
> 
> In a session trying to track down a problem related to a bad 
> cable, I found that:
>  
> tcpdump -i xl0 -v -v -v host pop.incentre.net 
> 
> So you can see that nearly half of the packets have bad
> checksums.  

As I recall, xl supports doing the checksums in the nic.  If all the
errors you're seeing are on xmit, it's because tcpdump is seeing the
packets before the checksums are computed.  At least that's what I
remember from some years ago when I had a 3com nic.

-- 
Barney Wolff         http://www.databus.com/bwresume.pdf
I'm available by contract or FT, in the NYC metro area or via the 'Net.