What could cause two devices to refuse to link?

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http://serverfault.com – This is a curious case where all the devices at hand will link with one another, except for two that just won't detect one another. One device is a single board computer (SBC) with a gigabit nic, the other is a fancy managed gigabit switch. If I patch the computer into any other switch (have two others models on hand in the lab), computer and switch link up fine. If I plug other computers into the finicky switch, they link up fine, too. But this one SBC just won't even get a link light on any port with the finicky switch - it's as though the cable I plugged in just isn't even there. It's not (HowTos)