Networking 101 - Switches

Submitted by tarvid on Sun, 05/18/2014 - 10:49

In a recent upgrade of Cox cable service in Fairfax, I installed a Linksys EtherFast® 10/100 5-Port Workgroup Switch. I naively plugged in cables connecting devices and when I plugged in the last one, my network died. This is a rather dumb switch, but if you look at the back there are 6 RJ45 ports on a 5 port switch.

I had connected the uplink correctly (sixth port) to my cable modem. When I plugged a device into the fifth port, I had two devices connected to the same port. Standard cables are wired straight through and are intended to connect a DTE (Data Terminal Equipment) such as a PC to DCE (Data Communications Equipment) such as a modem, switch or router. Newer equipment is smart enough to switch DTE and DCE automatically, but this switch depends on manually connecting to the correct port and leaving the corresponding port empty. I really needed to connect 5 DTE devices so the soltion was to install an 8 port switch to avoid the conflict.

Any plumber or farmer would know but network engineers cannot tell which sex a plug or jack is. RTFM!.