[lug] Basic Troubleshooting Skills

[David L. Anselmi]

John Dollison wrote:
> I was a Navy Electronic Technician for nine years, and you're not the first to ask this kind of
> question. I'd like some time to think about an answer (and review several Navy manuals in my
> basement), but I'll give you some quick thoughts now.

You know John, as I reread this it's a lot more insightful than you might think.  Practically a
mini-syllabus.  Thanks!  With your permission I'm going to use it next time I need to talk about
this sort of thing.

> Having a keen sense of observation
...
 > It helps if you're able to look for and recognize patterns.

Indeed, and this is especially true with computers, I think, where the patterns may be subtle but 
definitive.  I had an opportunity to play this trick on a Navy IT specialist:

   $ ping -n google.com
   PING google.com (10.0.0.5) 56(84) bytes of data.
   From 10.0.0.10 icmp_seq=1 Destination Host Unreachable
   From 10.0.0.10 icmp_seq=2 Destination Host Unreachable

Obviously 10.0.0.5 is not Google's address, so my name resolution is hosed (can you say /etc/hosts?)

In the actual case I had put in an incorrect, but similar looking, IP for a domain controller.  The 
IT didn't notice the address was wrong.  But "Destination Host Unreachable" is entirely different 
from "request timed out".  Unfortunately for the poor guy, although he had heard that Windows 
machines have an etc/hosts file, he had no idea how it related to name resolution so he had no 
chance of solving the problem.

I think it was a good learning experience for him.

Dave