Securing power to my Fiber modem/router

On my Fiber modem/router box there is a warning that says to keep it plugged in and powered at all times. I plan on installing a 240v outlet in my garage which will require me to secure power to my house while I install the new breaker. Are there any preparations I should make for my modem/router to make sure it works properly after I restore power to my house? I think that optimistically, I will need the power secured for about 30 minutes or so.