Selecting a Networking Scheme

Updated on 2024-09-24 GMT+08:00

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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.

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	In 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.	Connectivity between VPCs: Using an Enterprise Router to Enable Communications Between VPCs in the Same Region Connectivity between VPCs and an on-premises data center: Using Enterprise Router and Direct Connect to Allow Communications Between an On-Premises Data Center and VPCs	For details, see How Do I Select a Networking Scheme?
Scheme 2	In 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	For details, see How Do I Select a Networking Scheme?

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 ELB, VPC Endpoint, NAT Gateway (private NAT gateways), or DCS, contact customer service to confirm the service compatibility and preferentially use a transit VPC for networking.
- Traffic cannot be forwarded from a VPC to the enterprise router if you set the destination of a route in the VPC route table to 0.0.0.0/0 and:
  - 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, and 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.

NOTICE:

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

Next topic: Using an Enterprise Router to Enable Communications Between VPCs in the Same Region

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