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Remote-access software also requires that the network and the network stack be in working order. If a server loses its network connection, whether by OS failure, unplugged network link or failing network card, you're out of luck. An IP KVM, however, lets you access the server no matter what its software state, assuming the person who unplugged the network connection to the server left the KVM attached to the network. The devices we tested let us access the BIOS, boot into Windows safe mode and watch system shutdown messages. In addition, the devices from Avocent, Raritan, Cyclades, Minicom and StarTech can dial in over modems, so you might be able to reach remote devices and figure out what caused the network meltdown.

Architecture and Integration

KVMs once relied exclusively on proprietary cabling for carrying analog video and mouse-keyboard signals. Aten and StarTech sent us low-priced units with proprietary cabling. The other appliances we tested use digital signals carried over Category 5, Cat 5E or Cat 6 cable. We attached custom proprietary dongles to the video and keyboard ports on each of our servers, then connected a Cat 5 cable from each dongle to the KVM concentrator.

We prefer Cat 5 to proprietary cable, and not just for the obvious cost and convenience reasons. For one, Cat 5 may take up less space: Cyclades says it can carry a signal over 500 feet, and Minicom claims 660 feet (though we didn't test connections over more than the 100-meter spec). Also, note that we don't say "Ethernet cable"--we didn't plug the dongle into an Ethernet switch, but instead had to home run connections to the KVM concentrator. Data centers with properly designed and organized patch panels should handle this easily. A few years ago our Syracuse labs switched from a proprietary to a Cat 5-based KVM, and the move greatly simplified our lives.

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