Help Center/ Enterprise Router/ Getting Started/ Selecting a Networking Scheme
Updated on 2025-08-22 GMT+08:00
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Selecting a Networking Scheme

You can use enterprise routers to build a central network and to simplify the network architecture. There are two typical schemes to use Enterprise Router together with Direct Connect to allow an on-premises data center to access multiple VPCs. For details, see Table 1.
Figure 1 Networking for allowing an on-premises data center to access two service VPCs directly (scheme 1)
Figure 2 Networking for allowing an on-premises data center to access two service VPCs over a transit VPC (scheme 2)
Table 1 Comparison between the two schemes

Scheme

Networking Architecture

Network Path Description

Configuration Guide

Remarks

Scheme 1

Figure 1

Two service VPCs (VPC-A and VPC-B) and the Direct Connect virtual gateway are attached to an enterprise router.
  • The enterprise router enables the two VPCs to communicate with each other.
  • Direct Connect enables the on-premises data center to access the cloud, and the enterprise router connects the on-premises data center to both VPCs.

For details, see How Do I Select a Networking Scheme?

Scheme 2

Figure 2

The two service VPCs (VPC-A and VPC-B) are not attached to the enterprise router. Instead, a transit VPC (VPC-Transit) is used. The transit VPC and the Direct Connect virtual gateway are attached to the enterprise router.
  • Each service VPC is connected to the transit VPC over a VPC peering connection.
  • Direct Connect enables the on-premises data center to access the cloud, and the enterprise router connects the on-premises data center to the two service VPCs.

Using Enterprise Router and a Transit VPC to Allow an On-premises Data Center to Access Service VPCs

How Do I Select a Networking Scheme?

In scheme 1, the service VPCs are directly attached to the enterprise router. In scheme 2, a transit VPC is used and attached to the enterprise router. Each service VPC is connected to the transit VPC over a VPC peering connection. Compared with scheme 1, scheme 2 costs less and eliminates some constraints, 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.

If you still want to use scheme 1 to attach service VPCs to an enterprise router, contact customer service to evaluate the feasibility.