EC2 Instance migration from IPv4 to IPv6

Question

I am working on migrating 5 AWS instances from IPv4 to IPv6.  I have tried following the steps for this using
https://docs.aws.amazon.com/vpc/latest/userguide/vpc-migrate-ipv6.html#vpc-migrate-ipv6-cidr
but hit snags. It may be that the docs are intended for more complex scenarios than mine. I have a variety of t2 instances (5 of them) that are essentially standalone servers. I am only using subnets because AWS does so automatically. They are all in 1 VPC, and I have managed to assign an IPv6 CIDR to it.

The instructions say the next step is to associate an IPv6 CIDR block with a subnet (why do I only have 4 subnets for my 5 unrelated instances?).  But when I select a subnet, under Actions, "Edit IPv6 CIDRs" is disabled. What have I missed?

Accepted Answer

Thanks. I was in the middle of documenting that I HAD added IPv6 CIDRs to my VPC, and that my instance types DO support IPv6, when I decided to try again to assign IPv6 CDIRs to my subnets... and it allows it!  Maybe it just took some time for AWS to process my IPv6 CIDR assignments to my VPC?  If so that should be included in the docs so that we don't waste time trying to do something that doesn't work (yet?).

Answer

Hello.

"Edit IPv6 CIDRs" for a subnet cannot be selected unless an IPv6 CIDR is associated with the VPC.  
Have you selected a VPC subnet with an IPv6 CIDR?  
Please check the VPC ID carefully.

Answer

You **MUST add IPv6 CIDRs to your VPC** before editing subnet. 
And you need to check EC2 instances that support IPv6 or not.
You can check it on web console of EC2 Instance Types tab and filtering by "IPv6 support : -".

Answer

"Edit IPv6 CIDRs" will be enabled if your subnet's VPC has an associated IPv6 block.  It will only be disabled if the VPC has no associated IPv6 block.

EC2 Instance migration from IPv4 to IPv6

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