InternetGateway

Source: src/AWS/EC2/InternetGateway.ts

An internet gateway provides a target for internet-routable traffic in a VPC, enabling bidirectional IPv4 and IPv6 connectivity between resources in your VPC and the public internet. A VPC can have at most one internet gateway attached at a time.

The only inputs are the optional vpcId to attach to and tags. Attaching a gateway is not enough on its own to make a subnet public — you also need a 0.0.0.0/0 Route pointing at the gateway and a RouteTableAssociation binding the subnet to that route table.

Creating an Internet Gateway

Pass vpcId to create and attach the gateway in one step, or omit it to create a standalone gateway and attach it later by setting the prop. Updating vpcId moves the gateway between VPCs (detach then attach) without recreating it.

Internet Gateway Attached to a VPC

const internetGateway = yield* AWS.EC2.InternetGateway("InternetGateway", {
  vpcId: myVpc.vpcId,
});

Creates the gateway and attaches it to the VPC immediately. The resulting internetGatewayId (prefixed igw-) is what you reference from a route’s gatewayId.

Detached Internet Gateway

const internetGateway = yield* AWS.EC2.InternetGateway("InternetGateway", {});

Omitting vpcId creates an unattached gateway. This is occasionally useful when the VPC is provisioned separately; add the vpcId prop later to attach it.

Internet Gateway with Tags

const internetGateway = yield* AWS.EC2.InternetGateway("InternetGateway", {
  vpcId: myVpc.vpcId,
  tags: { Name: "production-igw" },
});

The tags map is merged with the alchemy auto-tags and can be changed in place. A Name tag makes the gateway easy to identify in the AWS console.

Enabling Public Internet Access

An internet gateway only carries traffic once a route table sends traffic to it and a subnet is associated with that table. The full pattern below makes a subnet public.

const internetGateway = yield* AWS.EC2.InternetGateway("InternetGateway", {
  vpcId: myVpc.vpcId,
});

const publicRouteTable = yield* AWS.EC2.RouteTable("PublicRouteTable", {
  vpcId: myVpc.vpcId,
});

const internetRoute = yield* AWS.EC2.Route("InternetRoute", {
  routeTableId: publicRouteTable.routeTableId,
  destinationCidrBlock: "0.0.0.0/0",
  gatewayId: internetGateway.internetGatewayId,
});

With the default route in place, any subnet associated with publicRouteTable can send and receive internet traffic. Add an analogous route with destinationIpv6CidrBlock: "::/0" to enable IPv6.