IPAM nested pool

Question

Ran into an issue today with CloudFormation and the new IPAM Pool. Trying to create a nested pool. The Parent pool creates just fine but when the Child pool tries to create it errors out. CloudTrail shows the error as: 'The sourcePoolId ipam-pool-01234567890abcdef has an AddressFamily ipv4 different from input AddressFamily IPv4'

From what I've troubleshoot and tested, CloudFormation only accepts IPv4 or IPv6 for the Address Family. The API only accepts ipv4 or ipv6. It looks like when CloudFormation queries the parent pool for its address family, it returns ipv4 (as expected) but when it compares it to what was provided in the validated template, they are not a match (different case).

Anyone else run into this or had similar results?

AWSomeCSS · Answer

This appears to be a case sensitivity issue between CloudFormation and the IPAM API, which is causing the validation to fail incorrectly. The error occurs because CloudFormation is doing a direct string comparison between:

1. The parent pool's address family (returned as "ipv4" in lowercase)
2. The template specification (using "IPv4" with different capitalization)

To resolve this issue, you could try:

1. In your CloudFormation template, specify the AddressFamily as "ipv4" (lowercase) instead of "IPv4"
2. If that doesn't work, you might need to file a support case with AWS as this appears to be a CloudFormation service issue where it's not handling case-insensitive comparison properly

This type of issue is something AWS should handle internally, and you may want to report it through AWS support or raise it on the AWS CloudFormation GitHub issues page as it appears to be a bug in how CloudFormation handles the IPAM API integration.

IPAM nested pool

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