👀 Views: 54 💬 Answers: 1 📅 Created: 2025-06-09

aws cloudformation vpc subnet YAML

I've tried everything I can think of but I'm getting frustrated with I'm working on a project and hit a roadblock... I'm attempting to create a VPC using AWS CloudFormation, but the stack fails with the behavior 'Resource creation failed'. The problematic resource appears to be the subnet. Here's a snippet of my CloudFormation template: ```yaml Resources: MyVPC: Type: AWS::EC2::VPC Properties: CidrBlock: 10.0.0.0/16 EnableDnsSupport: true EnableDnsHostnames: true MySubnet: Type: AWS::EC2::Subnet Properties: VpcId: !Ref MyVPC CidrBlock: 10.0.1.0/24 AvailabilityZone: us-east-1a MapPublicIpOnLaunch: true ``` I've verified that the CIDR blocks are correct and that the availability zone exists. I also tried changing the CidrBlock for the subnet to a different range within the VPC, but I still encounter the same behavior. Additionally, I have no conflicting resources in the same region. When I check the CloudFormation events, I see the following behavior message: ``` Resource status: CREATE_FAILED Resource type: AWS::EC2::Subnet Resource name: MySubnet Reason: The specified CIDR block is not valid for the VPC. ``` I suspect that there might be some inherent limits or specific configurations for subnets in this region that I'm missing. Could someone guide to troubleshoot this scenario? Are there any best practices for defining CIDR blocks in CloudFormation that I should follow? I'm working on a web app that needs to handle this. Hoping someone can shed some light on this. Thanks for your help in advance! I've been using Yaml for about a year now. Any feedback is welcome!