How can EC2 maintain IP addresses in a multi-AZ failover situation?

Question

A vendor provides a service to a single AWS region. A client of that vendor has an EC2 instance residing in a single AZ. The vendor's service is tied to an IP address for licensing purposes.

Now let's say that the AZ or specific EC2 fails.

I know that you can set auto scaling groups to spin up replacements for failed instances, but the IP address is going to be different and thus the vendor's license scheme will be a blocker.

I think I recall the ability to reserve a specific IP for EC2, but haven't touched that to-date. But that being said, can you use that reserved IP address across AZs?

So the question is, in the event of a failure of an EC2 instance in AZ1, can I have a specific IP address be picked up for a backup EC2 instance in AZ2?

Accepted Answer

You can use an [Elastic IP address][1] for this. It can be assigned across a region. To re-assign the Elastic IP address when an instance is 'lost', you can use CloudWatch Events.

[1]: https://docs.aws.amazon.com/vpc/latest/userguide/vpc-eips.html

How can EC2 maintain IP addresses in a multi-AZ failover situation?

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