Overview

You can use enterprise routers to build a central network and to simplify the network architecture. There are two typical networking schemes. One is to attach the service VPCs to the enterprise router. The other is to use a transit VPC to build a network, together with VPC Peering and Enterprise Router. Compared with scheme 1, scheme 2 costs less and eliminates some restrictions, as detailed below:

• Scheme 2 uses less traffic and fewer attachments.
  • Traffic between service VPCs is routed through VPC peering connections instead of enterprise routers, reducing traffic costs.
  • Only the transit VPC is attached to the enterprise router. You can pay less for the attachments.
• Scheme 2 frees you from the following constraints that scheme 1 has on attaching service VPCs to an enterprise router:
  • If a service VPC is used by a shared load balancer, VPC endpoint, private NAT gateway, or DCS resource, contact customer service to confirm the service compatibility and preferentially use a transit VPC for networking.
  • Traffic cannot be forwarded from a VPC to its attached enterprise router if the destination of a route with an enterprise router as the next hop is set to 0.0.0.0/0 in the VPC route table and if:
    • An ECS in the VPC has an EIP bound.
    • The VPC is being used by ELB (either dedicated or shared load balancers), NAT Gateway, VPC Endpoint, or DCS.
  • If a VPC attached to an enterprise router has a NAT gateway associated and Scenario of the SNAT or DNAT rules is set to Direct Connect, the network from the on-premises data center to the VPC is disconnected.

In scheme 2, service VPCs communicate with each other over VPC peering connections and with the on-premises data center using an enterprise router. Figure 1 shows the networking architecture.

1. Create a VPC peering connection between VPC-A and VPC-Transit, and between VPC-B and VPC-Transit. Traffic between VPC-A and VPC-B is forwarded through VPC-Transit and the two VPC peering connections.
2. VPC-Transit is connected to the enterprise router. Traffic from VPC-A and VPC-B to the on-premises data center is forwarded to the enterprise router through the transit VPC, and then to the on-premises data center over the Direct Connect connection.