RIR BGP Multi-Home between on-prem and AWS. *gulp*

Hi everyone!

I have a fortunate "problem" on my hands. I have a recent allocation of a /22 IPv4 from ARIN to use for some of our locations in a hybrid cloud environment.

My dilemma: What is the most efficient way to multi-home some of my IPs so that they are routable from one of my on-prem locations but "fail over" to AWS ASNs in the cause that my on-prem routing goes offline. AWS does not give much control over the RIR/Public ASN BGP settings with the BYOIP program.

My initial thoughts were to pull the whole /22 into AWS and then advertise a /24 out of the on-prem datacenter ASN (that is more than enough IPs at the moment). If my theory is correct, this route should supersede the /22 advertisement from AWS until the /24 goes offline. At that point, the /22 route will then function.

Anyone have any experience with this? Also, what does "fail back" look like when I re-introduce the /24 on the on-prem location?

Thanks in advance!