MacBook Air 2,1 external CD - Acting dead

I've had this issue before and thought I wrote down the answer, but I can't find it to save my life.

I have a MacBook Air 2,1 and the external CD/DVD drive. Occasionally, the drive will complete stop working. I've called support on this before and I was told to hold down three or four keys and reboot the Mac and it reset the power to the USB drive.

For the life of me, I can't find what those commands are called or what the multi-finger salute is to reset the drive.

Thanks for helping!