RouteTableAssociation

Source: src/AWS/EC2/RouteTableAssociation.ts

Associates a RouteTable with a subnet (or a gateway), making that route table govern traffic for the associated resource. A subnet can be associated with exactly one route table at a time; multiple subnets may share the same route table.

Provide exactly one of subnetId or gatewayId. Changing the subnet or gateway replaces the association, whereas pointing an existing association at a different route table is applied in place via ReplaceRouteTableAssociation.

Associating Subnets

Associating a subnet overrides the VPC’s main route table for that subnet. This is how you make a subnet “public” (associate it with a table that has an internet-gateway route) or “private” (associate it with a NAT-gateway table).

Associate a Subnet with a Route Table

const association = yield* AWS.EC2.RouteTableAssociation("PublicSubnetAssociation", {
  routeTableId: publicRouteTable.routeTableId,
  subnetId: publicSubnet.subnetId,
});

Binds a single subnet to the route table so its instances follow that table’s routes. The returned associationId (prefixed rtbassoc-) can be used to track or replace the association.

Share One Route Table Across Multiple Subnets

const subnet1Association = yield* AWS.EC2.RouteTableAssociation("PublicSubnet1Association", {
  routeTableId: publicRouteTable.routeTableId,
  subnetId: publicSubnet1.subnetId,
});

const subnet2Association = yield* AWS.EC2.RouteTableAssociation("PublicSubnet2Association", {
  routeTableId: publicRouteTable.routeTableId,
  subnetId: publicSubnet2.subnetId,
});

Declaring multiple associations against the same routeTableId gives every listed subnet identical routing — a concise way to apply one public (or private) routing policy across all subnets in a tier.

Associating Gateways (Edge Routing)

Instead of a subnet, an association can target an internet gateway or virtual private gateway via gatewayId. This “gateway route table association” enables edge routing, where inbound traffic is inspected or redirected (e.g. to a firewall appliance) as it enters the VPC.

const edgeAssociation = yield* AWS.EC2.RouteTableAssociation("EdgeAssociation", {
  routeTableId: ingressRouteTable.routeTableId,
  gatewayId: internetGateway.internetGatewayId,
});

Attaches the route table at the gateway rather than at a subnet, so traffic arriving from the internet is steered by this table — typically toward an inspection appliance before reaching its destination subnet.