Wiring matters20 Jan 2009
Most people think of the wiring in the office as "just some cables" that can easily be added to with a $20 hub or switch from the electronics store. In reality, proper wiring can make or break your network. Here are some of the problems I have come across over time:
- Using cheap equipment. One of my first customers ever was very budget-conscious, and I was not yet as experienced as I am today. I found a $19 no-name 16-port switch at an electronics store. Should have stopped to think about why it was so cheap. The next week, the customer kept calling me that the network was down and the computers kept crashing. As it turned out, one of the ports on this switch was so bad that it sent out signals throughout the network.
- Home-made wiring. Another of my customers wanted to save money and did all the wiring in his new office himself. He kept calling me about "why is the network so slow. I've got CAT 6 cable and a Gigabit switch". Eventually, he found the problem himself: he had crosswired some of the cables. They still worked, but caused transmission errors.
- Poorly run wiring. A third of my customers got regular transmission errors on the network. We tracked it down to the fact that his wiring contractor had run the Ethernet cables parallel to a power cable.
- "Adding more outlets" with a cheap $20 hub or switch from the electronics store. Granted, sometimes it is unavoidable, but it also causes any number of problems. Here are just a few of the problems this causes:
- Such a hub becomes a single point of failure - and, being cheap, they do fail quite frequently
- Some people do not know the difference between a hub, a switch and a router and plug in a router instead of a switch. At one of my customers, one of the somewhat tech-savvy people did exactly this - but forgot to change the IP address for the router. As a result, their real Internet router had the same IP address (192.168.0.1) as this extra router. Internet traffic was erratic at best. Even worse, this router still had the DHCP server enabled.
- Sometimes, it is necessary to force workstations in a network to renew their IP addresses immediately. The easiest way to do this is to remove the network cable, and plug it back in a few seconds later. If you need to reconfigure a complete network this way, you can simply power down the main switch for the same effect throughout the network. However, local switches at the workstation side of the connection disable this mechanism.
- Using too long cables, or cables that are bent. One of my customers complained that a few of the workstations were very sluggish some days, blazingly fast on others. Fortunately, the customer had a managed switch with a cable testing feature that was able to show me the problem. Those computers that were blazingly fast reported a cable length between 30 and 80 feet - expected for the size building. Those computers that were slow reported an "unknown cable length". In one case, the cable from the wall outlet to the workstation was a badly kinked and coiled up cable of probably at least 100 ft. Replacing it with a brand-new 25-ft CAT 6 cable solved the problem.