Allied Telesis AT-8900 Series Troubleshooting page 5

Providing a convincing case
If you believe that you have successfully hit on the right theory, and have isolated what
appears to be a good candidate for the root cause of what is going wrong, gather as much
evidence as you can to support the theory.
Concrete piece of advice #6: If you find a sequence of actions that make
the problem happen, capture the full sequence (and the evidence that
the problem has happened) multiple (more than 2) times if possible.
Often certain pre-conditions are pertinent to the circumstances in which the problem will or
won't occur—'the problem still occurs even if port 2 is not connected'; 'if the ARP entry has
been cleared before the route ages out, the problem does not happen' etc. It is important to
capture the output to illustrate these pre-conditions—it might be very clear to you that port
2 is definitely disconnected, but the person analysing the captures after you might not truly
believe that unless they see the output of the show port command that shows port 2 to be
DOWN.
Concrete piece of advice #7: Capture as much evidence as possible to
support any assertions you make about the circumstances in which you
see the problem happen.
Annotating afterwards
Before you send your capture off to the next layer of support or anyone else, you will want
to give them as much guidance as possible as to how to extract the significant pieces of
information from your capture. This can be achieved by going through the capture and
putting in further comments to spell out more clearly what is happening than you were able
to do with the quick comments you typed in while on-site. Or, you might want to copy the
really important parts out of the capture and paste them into a separate file, to succinctly
illustrate the core of the problem.
Concrete piece of advice #8: Some post-processing of the capture file
can save a lot of time and effort for anyone who is analysing it after you.
But, even if you copy the pertinent pieces out of the capture, still send the rest of the capture
file anyway, there could be significant gems of information in there that you weren't aware of.
Concrete piece of advice #9: If possible, always send everything that
you captured—too much information is always better than too little.
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