6509, and pull it out of the power supply. Of course, the 6509 AC power supplies allow the power cables to be secured with clamps, but the last engineer to work on the switches forgot to retighten the clamps. Each 6509 has two power supplies, which are connected to different circuits, SO pulling one power cord should not be an issue. However, the engineer who forgot to retighten the clamps decided that the cables would look neater if he wire-tied them together. When I tripped over the cable, it was really both cables bound together, which means I ended up unplugging all the power from the 6509 that was supporting the network. The result: complete network failure. To recap, the following combination of events caused the outage: I was born completely without grace or coordination. The last engineer to work on the system tied the power cords together and left them out where I could trip on them. The last engineer did not tighten the AC power cord clamps to the power supplies. I shut down one 6509. I tripped over the cords to the remaining 6509. Any one of these events in isolation would not have caused an outage. In fact, any two would probably not have caused an outage. If the power cords had been left unclamped, Disaster Chains but the cables were not tied together, my big clown-size feet would probably have only pulled one cable, leaving the switch with one active power supply. Disaster chains can take some digging to uncover. In the case of me tripping over the power cord, the exec who was grilling me asked, "How could this happen?" Having an answer to a question like this can save your job, especially when the answer appears to be as simple as you being a klutz. No Failover Testing I once worked with a team designing a large ecommerce website infrastructure. When I say large, I mean eight Cisco 6509 switches serving more than 200 physical servers (most with multiple virtual machines), providing upward of a gigabit per second of content. Timelines were tight, and everyone was stressed. In all the compression of 