CreateVPC can't create IPv6 only VPC

[aRustyDev]

Describe the bug

$ aws ec2 create-vpc --ipv6-ipam-pool-id <ipam-pool-id> --ipv6-netmask-length 56

An error occurred (MissingParameter) when calling the CreateVpc operation: Either 'cidrBlock' or 'ipv4IpamPoolId' should be provided.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

Should successfully create an IPv6 Only VPC

Following the directions from a terraform managed terraform-module for creating a VPC also fails (b/c its likely an API/CLI issue)

Current Behavior

$ aws ec2 create-vpc --ipv6-ipam-pool-id <ipam-pool-id> --ipv6-netmask-length 56

An error occurred (MissingParameter) when calling the CreateVpc operation: Either 'cidrBlock' or 'ipv4IpamPoolId' should be provided.

Reproduction Steps

1. create a IPv6_IPAM_Pool independently
2. Get the Pool Id of the above
3. run aws ec2 create-vpc --ipv6-ipam-pool-id <ipam-pool-id> --ipv6-netmask-length 56

Possible Solution

No response

Additional Information/Context

No response

CLI version used

aws-cli/2.11.8 Python/3.11.2 Darwin/24.4.0 exe/x86_64 prompt/off

Environment details (OS name and version, etc.)

Darwin mybox 24.4.0 Darwin Kernel Version 24.4.0: Fri Apr 11 18:28:23 PDT 2025; root:xnu-11417.101.15~117/RELEASE_X86_64 x86_64

[aRustyDev]

for anyone whose experiencing a similar issue, I created a ticket on hashicorp/terraform-provider-aws as well
link

[aRustyDev]

Also found this "similar" issue here, I'm going to follow its recommendations as well.

[adev-code]

Hello @aRustyDev, thanks for reaching out. I have replicated the command above aws ec2 create-vpc --ipv6-ipam-pool-id <ipam-pool-id> --ipv6-netmask-length 56 and got the same issue. I am not a VPC service expert but I created a ticket to the VPC service team for clarification on whether or not they are needed (as it looks like the parameters are needed) and asked for API documentation to be updated. I will update if there are any updates. Thank you.

For Internal Tracking: P232150481

[adev-code]

Hello @aRustyDev , thanks for the patience. The team has clarified that the service don't support IPv6-only VPCs right now, only IPv6-only subnets. The validation error that you are seeing is from the service server-side, not CLI. As per the service, 'cidrBlock' or 'ipv4IpamPoolId' should be provided. Please let me know if you have any questions. Thank you.