I consider myself fairly technical, and reasonably competent in the systems that I support. I’m not an expert, but you can see my thoughts on that in some other blog post
That said, it’s interesting how sometimes, particularly in the troubleshooting process, I find myself suffering from ‘tunnel vision’ and missing things that would normally be obvious to me. I spent a few hours today working on troubleshooting some call routing issues with a T1 CAS interface on a Cisco voice gateway, and for the life of me, I could not get the right dial peers to match, and the call to route properly. I was banging my head against the wall, because i “KNEW” that everything was set up the way it should be. But really, I was suffering from tunnel vision. The actual solution to my problem was trivial.
I think what happens is that the more we learn about a technology, the more our brains start jumping from A to D, without passing through B and C, or in other worse, we make assumptions. We get tunnel vision and skip steps in the troubleshooting process, and the most simple of things smack us in the face.
So what is the solution? Trust nothing, and prove everything. Debugs and wireshark are your friend. Don’t assume.