[sdnog] Common problem in sudan | Duplex mismatch

Scott Weeks surfer at mauigateway.com
Wed Jan 28 00:10:40 SAST 2015

Hello Bernd,

--- bernd.spiess at de-cix.net wrote:
From: Bernd Spiess <bernd.spiess at de-cix.net>

> good point ... in general there is no magic - the problem 
> is quite standard on 100 MBit interfaces when you donĀ“t
> define if you connect auto to auto or manual to manual - 
> if you try to mix auto negotiate with manual duplex you
> have for sure this problem.

In my case it was not auto on one side and hard coded
on the other.  It was auto on both sides. And what was 
stranger (I have seen this more than once on this network) 
is no work was being done on either device.  For some 
reason, the two devices decided to re-negotiate and come up 
with silly decisions, such as 100/half.  

> last: if you have performance problems - as you said: you 
> can in many cases bet on a duplex problem in your network...
> ... and this is also one of the reasons why your switches 
> should be in all cases manageable...

One way to watch for this is have all devices send syslog 
messages to one central syslog server and then watch the 
logs on the server for anything unusual.  It allows you to 
look at your entire network from one screen.  If anyone's 
interested in how to make that happen let me know and I will 

> PS: keep up that great work - quite a perfect mailing list 
> with very good discussions :-)

Yes, I am looking forward to learning a lot from this new 
list! :-)


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