Pulling out the wrong networking cable can be a bad idea!

A few years ago I showed up, filled with excitement, at the offices of our first ever user. Our software was just an alpha back then, and I came in with an HP Proliant server pre-installed with it. My contact at the customer walked with me to the data center and pointed to the rack we were going to set up the server in.

10 minutes later, the server was racked and hooked up to power. Now, we only needed to connect it to the network. We ran a network cable from the server to the top-of-rack switch, but alas - the switch didn't have any available ports! My contact looked at the switch, looked at the cables hanging down from it, and picked one cable that he thought wasn't connected to anything.

We disconnected that cable from the TOR switch and connected the Indeni server.

Within 30 seconds, three guys came running into the data center. Their faces were pale-white. Apparently we took down the out-of-band monitoring and management network, by disconnecting it from the main firewall. Oops!