Error while creating Vpc with one subnet which has the same cidr range

[dennisfleischmann]

Hi together,

I might wonder how to create one vpc with exactly one subnet which has the same cidr range. I tried the following

            vpc = ec2.Vpc(self, "vpc-with-one-subnet-and-one-cidr-example",
                ip_addresses=ec2.IpAddresses.aws_ipam_allocation(
                    ipv4_ipam_pool_id=ipam_pool,
                    ipv4_netmask_length=27,
                ),
                max_azs=1,
                subnet_configuration=[
                    ec2.SubnetConfiguration(
                        name = 'Public-Subnet-1',
                        subnet_type = ec2.SubnetType.PRIVATE_ISOLATED,
                        cidr_mask = 27,
                    ),
                ]
            )

This is Synthesizing without Erros but when I deploy it -- it will fail.

Note: When I change the cidr range in the subnet to 28 -- it is working fine. But I need to create a vpc with 27 and a subnet with the same.

Error Log
`
8:01:48 AM | CREATE_FAILED | AWS::EC2::Subnet | apptenantvpcexampl...net1Subnet43A66E78
Template error: Conversion = s, Flags = 0

❌ app-tenant failed: Error: The stack named app-tenant failed to deploy: UPDATE_ROLLBACK_COMPLETE: Template error: Conversion = s, Flags = 0
at FullCloudFormationDeployment.monitorDeployment (/usr/local/lib/node_modules/aws-cdk/lib/api/deploy-stack.ts:505:13)
at processTicksAndRejections (node:internal/process/task_queues:96:5)
at deployStack2 (/usr/local/lib/node_modules/aws-cdk/lib/cdk-toolkit.ts:241:24)
at /usr/local/lib/node_modules/aws-cdk/lib/deploy.ts:39:11
at run (/usr/local/lib/node_modules/p-queue/dist/index.js:163:29)

❌ Deployment failed: Error: Stack Deployments Failed: Error: The stack named app-tenant failed to deploy: UPDATE_ROLLBACK_COMPLETE: Template error: Conversion = s, Flags = 0
at deployStacks (/usr/local/lib/node_modules/aws-cdk/lib/deploy.ts:61:11)
at processTicksAndRejections (node:internal/process/task_queues:96:5)
at CdkToolkit.deploy (/usr/local/lib/node_modules/aws-cdk/lib/cdk-toolkit.ts:315:7)
at initCommandLine (/usr/local/lib/node_modules/aws-cdk/lib/cli.ts:358:12)

Stack Deployments Failed: Error: The stack named app-tenant failed to deploy: UPDATE_ROLLBACK_COMPLETE: Template error: Conversion = s, Flags = 0
`

[dennisfleischmann]

Still thinking about a solution.From my understanding at least 2 subnets needs to be creates hence one subnet with the same cidr of the vpc is not possible. Happy to hear suggestions.