Whether it’s a copper network cable connecting your computer to a router, a fiber optic cable connecting an ISP to the Internet, or a microwave beam between two antennas, lack of respect for the physical layer (Layer 1 of the OSI model) has perpetuated more problems than I care to count.
So why start at Layer 1? It’s usually the easiest to diagnose! How many times have you heard someone ask, “Is it plugged in?” when an appliance isn’t working. It’s no different when working a network issue. Knock down the simple potential problems first, then move up to the more complex possibilities.
At a former employer, we received a call from a client that was experiencing intermittent loss of connectivity to one of their remote offices. They had a T-1 connection between the offices and it would cut in and out on a daily basis. We investigated a bit and found the far-end device was incrementing errors like crazy. After several days of back-and-forth with the telco service desk, a few trips with multiple engineers to each site (a several hour drive each way), and an unbearable number of conference calls later, we stumbled upon the problem. While talking one of the client’s staff through tracing a wire, the connection cut out and came back. On a hunch, we asked him what he had just touched. It was the serial cable connecting the router to the CSU/DSU at the local site. Someone hadn’t screwed down the connector and it had worked itself just loose enough to make for a flaky connection. 30 seconds and two tightened screws later, the connectivity issue was fixed.
Of course, there’s always the temptation to jump right into it and start hacking and modifying settings. It’s much more rewarding when you can show off your talent and come out victorious with some intricately detailed and elegantly complex solution to the problem. It’s critical to fight back the urge to miraculously save the day because it will affect your ability to diagnose the problem.
In fact, just recently I had a client who was experiencing significant call quality issues with their VoIP system. I had helped them get set up on a new ISP, and had implemented some basic Quality-of-Service features to help protect their voice traffic. Everything seemed fine at the time, but after a couple of weeks the staff started complaining of unacceptable static and dropped calls on their phones. The fix: swap out some old and beat-up Cat5 cables for newer Cat5e cables.
The next time you’re confronted with a network problem, make sure you double-check your connections first! If you’re in the business of hooking up a lot of equipment, invest in a decent cable tester. I’m partial to Fluke and would love to own one of these, but even $250 invested in a nice wiremap/toner/tester package will pay for itself many times over.
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