Any plans to support explicit cidrs ranges within VPC?

[moatazelmasry2]

So I had a requirement from a customer to create a VPC with specific CIDRs for the subnets. While I'm able to provide subnet configuration within a vpc and provide a netmask for public/private subnets, I'm not able to specify the exact cidr range within the subnet configuration.

I solved my problem by just creating every element in the vpc by hand, which is not ideal tbh. Here's my actual solution:

export class NetworkSetupStack2 extends cdk.Stack {
    constructor(scope: cdk.Construct, id: string, props: AccountSetupProps) {
        super(scope, id, props);
        const context = props.context
        const vpc = new ec2.Vpc(this, 'VPC2', {
            cidr: "10.249.0.0/21",
            maxAzs: 3,
            subnetConfiguration: []
        });
        const publicSubnet2a = new ec2.PublicSubnet(this, "PublicSubnet2a", {
            cidrBlock: "10.249.6.0/28",
            vpcId: vpc.vpcId,
            availabilityZone: "eu-central-1a"
        })
        const privateSubnet2a = new ec2.PrivateSubnet(this, "PrivateSubnet2a", {
            cidrBlock: "10.249.0.0/23",
            vpcId: vpc.vpcId,
            availabilityZone: "eu-central-1a"
        })
        const internetGateway = new ec2.CfnInternetGateway(this, 'InternetGateway', {
        })
        const att = new ec2.CfnVPCGatewayAttachment(this, 'VPCGatewayAttachement', {
            internetGatewayId: internetGateway.ref,
            vpcId: vpc.vpcId
        })
        publicSubnet2a.addDefaultInternetRoute(internetGateway.ref, att)
        const natProvider = ec2.NatProvider.gateway()
        natProvider.configureNat({
            vpc: vpc,
            natSubnets: [publicSubnet2a],
            privateSubnets: [privateSubnet2a]
        })
  }
}

Use Case

In an enterprise environment, you get certain IP ranges allocated by the enterprise and you sometimes need to map those ranges in a very specific way. An automatic distribution by aws cdk is not precise enough.

Proposed Solution

const vpc = new ec2.Vpc(this, 'VPC2', {
            cidr: "10.249.0.0/21",
            maxAzs: 3,
            subnetConfiguration: [
                {
                    cidrMask: 23,
                    subnetType: SubnetType.PRIVATE,
                    Subnets: [
                        {
                            name: "PrivateSiubnet1a"
                            cidrRange: "10.249.0.0/23",
                            availabilityZone: "eu-central-1a"
                        },
                        {
                            name: "PrivateSiubnet1b"
                            cidrRange: "10.249.2.0/23",
                            availabilityZone: "eu-central-1b"
                        },
                        {
                            name: "PrivateSiubnet1a"
                            cidrRange: "10.249.04.0/23",
                            availabilityZone: "eu-central-1c"
                        }
                    ]
                }
            ],
            natGateways: 3
        });

Other

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

---

This is a 🚀 Feature Request

[rix0rrr]

Duplicate: #7073
Related: #5927