問題文
An operator replaces one of the two power supplies of an access switch by inserting the new one and pulling the old one out immediately afterwards. The powered devices on the switch go down. What does the documentation say about this, and what should have been done?
選択肢
- A switch reads a supply as absent for 90 seconds after it has been pulled, so the budget falls to what one supply carries and the interfaces of the lowest priority are shed until the new supply has been recorded.
- A swap finished in under 25 seconds takes every powered device down, and the documented order is to insert the redundant supply first and leave it in place for at least 35 seconds before the other one is pulled.
- The budget is worked out again only at the next reboot of the switch, so the switch went on charging interfaces against the supply that had been removed until the last of the 500 watts it had on record was gone, at which point the interfaces began to fall in the order of their priority.
- The controller reloads its own software whenever the count of supplies changes, and no interface is guaranteed power for as long as ten minutes while that runs.