[En-Nut-Discussion] Strange networking bug - perhaps duplicate MAC

[Brett Abbott]

Curtis

Im unsure if youve had a response on this one and you can see Im a bit 
behind in my emails but....

This symptom is similar to what you see when your ethernuts have the 
same MAC address.  This is worth checking, especially if you hard code 
your MAC address into the source.

This probably wont be an issue if the units are in different physical 
networks and activity can differ depending on switch and gateway 
configuration.

Cheers
Brett

Curtis Maloney wrote:
> Sadly, I don't have much information on the specific cause, but I think 
> people should be aware of this instance.
>
> We had two X-Nuts running Nut/OS 4.1.9.  One unit had happily been 
> ticking away on the network for some time, the second added only recently.
>
> Suddenly, as we were preparing final tests before a major go-live, they 
> both stopped talking.  But not quite.  And not stopped working.
>
> Basically, the core thread of the application was still churning away, 
> polling devices on the serial port.  So, at least that much was ok.
>
> If I telnetted to them, I'd either get immediately disconnected, or get 
> one line of feedback, and then dropped.
>
> Our current theory is that some "poison packet" caused the TCP task to 
> go into a strange state.  Our reasoning is as follows:
>
> 1) The two units are geographically separate.  They reside in different 
> buildings approx 100m apart.  So it wasn't likely to be a local noise 
> glitch.
> 2) One unit had been reset earlier that day, whilst the other had been 
> on for several days.  So it wasn't a slow leak or time based issue.
> 3) Both units went at the same time, and exhibited EXACTLY the same 
> behavior.
>
> I haven't, as yet, had any time to devote to tracing my way through the 
> networking stack to find what could have possibly gone wrong. 
> Hopefully, though, this message might remind someone of something they 
> thought previously was harmless, or unlikely.
>
> Of course, if there's been significant changes between 4.1.9 and 4.2 TCP 
> code, maybe the fault is already gone...
>
>
> --
> Curtis Maloney
> cmaloney at cardgate.net
>
> _______________________________________________
> En-Nut-Discussion mailing list
> En-Nut-Discussion at egnite.de
> http://lists.egnite.de/mailman/listinfo/en-nut-discussion
>
>
>   

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Brett Abbott, Managing Director, Digital Telemetry Limited
Email: Brett.Abbott at digital-telemetry.com
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