FC2 - Strange Ethernet Behavior

[John Meagher]

John Krische wrote:

> Hello again to all
>
> Followup info on the networking problem I'm getting on FC2 (connection 
> speed plummeting for no apparent reason after ~1MB of sustained 
> traffic).  I've managed to rule out our main router and firewall as a 
> potential source, as the problem is appearing between hosts on the 
> internal LAN, going through a very nice switch.  I've also ruled out 
> the TCP Window Scale suggestion by Andy Green - tried various network 
> ops (internal LAN) with and without scaling, no effect whatsoever.  I 
> have further confirmed 100% that the problem is restricted to our FC2 
> boxes only.  We have a Debian box that is running kernel 2.6.7, same 
> as the FC2's, and is using the same NIC model & module as at least one 
> of our FC2's, but that debian system has none of these strange network 
> behaviors.
>
> Any other suggestions, anyone?
>
> John K.

You seem to have been pretty methodical about this.  You didn't mention 
anything about messages in /var/log/messages, though.  Often there's a 
clue there, if syslog.conf is set up to allow it.
Maybe if you ran ethereal or tethereal on the machine while it's being 
slow you could learn which end is  waiting for what.