How can I move EC2 instances to a different subnet?

Question

I have a VPC set up in AWS. we have created 2 subnets (A/24 and B/24), straight using all the IP having no IP's/Subnets for further usage.

We find that the b/24 is not totally utilized and we are wasting the Ip address in that.

Now we want to reduce the subnet size and move the instances from B/24 to A/24. and create 4 smaller subnets from B/24 and of /28 range and move back the servers to one of the smaller subnets created.

Please advise what are the suggested best practices we can apply in a way that we should be able to keep our available servers in B/24 and create multiple subnets as well.

Answer 1

As of now, I don't believe, moving a running machine is between subnets is possible. What you can do is, taking an image of it, shutting it down and then launching a new instance from the image in another subnet. This should work for you.

Answer 2

You can create a new VPC with the right subnet design. Then you can move the EC2 instance to a subnet in the new VPC. I wrote a tool to move an EC2 instance to another Subnet, AZ, VPC, AWS Region or AWS Account with one click. The tool is available for free at https://www.kopicloud.com/app/Move-EC2