avoiding double bookings between airbnb and vrbo

I only have three units, so I need to use the channel bridge for syncing with vrbo.

I'm ready to add one of my units on airbnb, will the ical links that do the calendar syncing allow me to somehow block vrbo if a new rental happens on airbnb, or the reverse where I block airbnb if one rents on vrbo?

Or am I stuck needing to do this manually, which means if a booking happens when I'm on a plane or away from a computer I can get double booked?

there is a setting on these sites that allows you to sync with other sites to avoid this. But it might be iCal, but should eliminate most problems. I think Booking.com has it too.

Yep, iCal is what you want here -- that will auto block off the calendars. We update every 30 minutes, channels tend to update several times a day but don't publish their schedules.

Each channel API integration also has its own separate method of updating calendars automatically, and those are up to the minute.