[PLUG] Network issues

Mike Connors mconnors1 at gmail.com
Thu Jan 21 19:25:01 PST 2010


Denis Heidtmann wrote:
> I am glad you have focused on this.  Since it is the only thing I have
> found which is consistently different between failed and working
> modes, it deserves some scrutiny.  I think it is interesting that the
> unused capability (1000baseT) is what is missing when in the failed
> mode.  Does it mean that the negotiation failed at that point?  Is
> there any way to snoop on the negotiation process?  I have wireshark,
> but am not familiar with running it.
>
> Thanks for you interest.
>
> -Denis
Argh, I'm baffled by this auto-neg behavior because why does it only 
happy once in blue moon and only upon booting. So yeah, you could use 
tcpdump and filter on any traffic for that eth interface. But I suspect 
by the time you get it setup the problem will have already occurred.

What might be a simpler and possibly more effective is to use ethtool to 
restart auto-neg and tail the log file and capture the auto-neg mssgs. 
See link below for how-to. Then when the networking fails, cat the log 
file and grep for any mssgs for that eth interface.

http://www.cyberciti.biz/tips/linux-network-card-restart-autonegotiation.html



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