Route Tables

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Route Tables

A route table contains a set of rules, called routes, that are used to determine where network traffic is directed.

Each subnet in your VPC must be associated with a route table; the table controls the routing for the subnet. A subnet can only be associated with one route table at a time, but you can associate multiple subnets with the same route table.

• Your VPC has an implicit router.

• Your VPC automatically comes with a main route table that you can modify.

• You can create additional custom route tables for your VPC.

• Each subnet must be associated with a route table, which controls the routing for the subnet. If you don't explicitly associate a subnet with a particular route table, the subnet is implicitly associated with the main route table.

• You cannot delete the main route table, but you can replace the main route table with a custom table that you've created (so that this table is the default table each new subnet is associated with).

• Each route in a table specifies a destination CIDR and a target (for example, traffic destined for the external corporate network 172.16.0.0/12 is targeted for the virtual private gateway). We use the most specific route that matches the traffic to determine how to route the traffic.

• CIDR blocks for IPv4 and IPv6 are treated separately. For example, a route with a destination CIDR of 0.0.0.0/0 (all IPv4 addresses) does not automatically include all IPv6 addresses. You must create a route with a destination CIDR of ::/0 for all IPv6 addresses.

• Every route table contains a local route for communication within the VPC over IPv4. If your VPC has more than one IPv4 CIDR block, your route tables contain a local route for each IPv4 CIDR block. If you've associated an IPv6 CIDR block with your VPC, your route tables contain a local route for the IPv6 CIDR block. You cannot modify or delete these routes.

• When you add an Internet gateway, an egress-only Internet gateway, a virtual private gateway, a NAT device, a peering connection, or a VPC endpoint in your VPC, you must update the route table for any subnet that uses these gateways or connections.

• There is a limit on the number of route tables you can create per VPC, and the number of routes you can add per route table