Help debugging network problem

[Michael Peek]

Hi gurus,

I have a machine running 2.6.24-19-server from the amd64 version of 
8.04LTS, and I have a strange networking problem.  Periodically (every 
few minutes) the network connection will stop working.  The strange 
thing is that 50% of the time, any active SSH connections to the machine 
continue to work, I can ping the machine from the outside, but new 
connections don't happen.

As an example:

In one window I ran tcpdump, while in the other window I attempted to 
use apt-get to install a package.  Apt said it was attempting to contact 
http://us.archive.ubuntu.com, but no packets showed up in tcpdump.  
Eventually
 apt quit with "Could not resolve 'us.archive.ubuntu.com'", and when I 
quit tcpdump it said: "664 packets dropped by kernel"

The network will work for a few minutes, then seize up for a few 
minutes, then magically start working again -- for a few minutes.  
During the network blackout, I can bring things back by ifdown/ifup the 
interface.  Then things will work again -- for a few minutes.

The ethernet is built in to a SuperMicro X7DWE, and is an Intel 
82563EB.  I tried both the e1000 driver that came with the stock kernel, 
and compiled the newer version that came on the motherboard driver CD.

Anybody have any idea why the kernel would drop packets?  Is this a 
driver issue, a hardware failure, or something completely different?


Thanks for your help!

Michael