Help Center/ Enterprise Router/ Best Practices/ Connecting Multiple On-Premises Networks in the Same Region Through Enterprise Routers/ Network and Resource Planning
Updated on 2026-03-16 GMT+08:00
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Network and Resource Planning

To use an enterprise router to allow on-premises networks in the same region to communicate with each other, you need to:
  • Network Planning: Plan the required Direct Connect global DC gateways, virtual interfaces, and enterprise router route tables.
  • Resource Planning: Plan the quantity, names, and other parameters of cloud resources, such as Direct Connect connection, and enterprise router.

Network Planning

Figure 1 shows the network planning for communications between on-premises networks in the same region. Two on-premises data centers are connected to the enterprise router through Direct Connect. Table 2 describes the details.

Figure 1 Communications between multiple on-premises data centers in the same region
Table 1 Network traffic flow description for communications between multiple on-premises data centers in the same region

Path

Description

Request traffic: from IDC-A, ER-A, to IDC-B
  1. In the route table of ER-A, there is a route with DGW-B attachment as the next hop and 192.168.3.0/24 as the destination to forward traffic to global DC gateway DGW-B.

    For the routes with DGW-B attachment as the next hop, 192.168.3.0/24 is the CIDR block of IDC-B and 10.182.0.0/30 is the gateway address of virtual interface VIF-B.

  2. Virtual interface VIF-B is connected to global DC gateway DGW-B to forward traffic from the remote gateway to the Direct Connect connection DC-B.
  3. The traffic is then sent to IDC-B through Direct Connect connection DC-B.

Response traffic: from IDC-B, ER-A, to IDC-A
  1. In the route table of ER-A, there is a route with DGW-A attachment as the next hop and 10.1.123.0/24 as the destination to forward traffic to global DC gateway DGW-A.

    For the routes with DGW-A attachment as the next hop, 10.1.123.0/24 is the CIDR block of IDC-A and 10.0.0.0/30 is the gateway address of virtual interface VIF-A.

  2. Virtual interface VIF-A is connected to global DC gateway DGW-A to forward traffic from the remote gateway to the Direct Connect connection DC-A.
  3. The traffic is then sent to IDC-A through Direct Connect connection DC-A.
Table 2 Network planning description for communications between multiple on-premises data centers in the same region

Resource

Quantity

Description

Enterprise router

1

Table 3 shows the route information of the enterprise router.

Enable Default Route Table Association and Default Route Table Propagation for the enterprise router so that routes with destinations set to attachments are automatically added when you create attachments for the enterprise router.

Direct Connect

2

The required Direct Connect resources in region A are as follows:

  • There are two connections that are created over leased lines provided by a carrier. Each connects an on-premises data center to the cloud. In this example, the two connections are DC-A and DC-B.
  • There are two global DC gateways. Each is attached to an enterprise router. In this example, DGW-A and DGW-B are attached to the enterprise router.
  • There are two virtual interfaces. Each connects a global DC gateway to a connection. In this example, the two virtual interfaces are VIF-A and VIF-B.
Table 3 Enterprise router route table

Destination

Next Hop

Route Type

CIDR block of IDC-A: 10.1.123.0/24

DGW-A attachment: er-attach-dgw-A

Propagated route

Gateway of virtual interface VIF-A: 10.0.0.0/30

DGW-A attachment: er-attach-dgw-A

Propagated route

CIDR block of IDC-B: 192.168.3.0/24

DGW-B attachment: er-attach-dgw-B

Propagated route

Gateway of virtual interface VIF-B: 10.182.0.0/30

DGW-B attachment: er-attach-dgw-B

Propagated route

Resource Planning

An enterprise router and its Direct Connect connections must be in the same region but can be in different AZs.

The following resource details are only for your reference. You can modify them if needed.

Table 4 Resource planning for communications between multiple on-premises data centers in the same region

Resource Type

Quantity

Description

Enterprise router

1
In this example, create an enterprise router and create two global DC gateway (DGW) attachments for it.
  • Name: Set it as needed. In this example, ER-A is used.
  • ASN: The ASN of the enterprise router must be different from those of on-premises data centers and global DC gateways. In this example, 64522 is used.
  • Default Route Table Association: Enable this option.
  • Default Route Table Propagation: Enable this option.
  • Auto Accept Shared Attachments: Set it as needed. In this example, enable this option.
  • Attachment: Two attachments are required for the enterprise router. In this example, the attachments are as follows:
    • Global DC gateway attachment er-attach-dgw-A that connects on-premises data center IDC-A to enterprise router ER-A
    • Global DC gateway attachment er-attach-dgw-B that connects on-premises data center IDC-B to enterprise router ER-A

Direct Connect

2

Two connections are required.

In this example, create connections DC-A and DC-B in region A.
Create two global DC gateways.
  • Name: Set it as needed. In this example, DGW-A and DGW-B are used.
  • BGP ASN: The ASN of a global DC gateway must be different from that of its enterprise router. In this example, the ASN of DGW-A is 64512, and that of DGW-B is 64513.
  • IP Address Family: Set it as needed. In this example, IPv4 is used.
Create two virtual interfaces.
  • Name: In this example, the two virtual interfaces are VIF-A and VIF-B.
  • Virtual Interface Priority: In this example, Preferred is selected.
  • Connection: In this example, virtual interface VIF-A is associated with connection DC-A, and VIF-B is associated with DC-B.
  • Global DC Gateway: In this example, virtual interface VIF-A is associated with global DC gateway DGW-A, and VIF-B associated with DGW-B.
  • Local Gateway: In this example, the local gateway IP address range for virtual interface VIF-A is 10.0.0.1/30, and that for VIF-B is 10.182.0.1/30.
  • Remote Gateway: In this example, the remote gateway IP address range for virtual interface VIF-A is 10.0.0.2/30, and that for VIF-B is 10.182.0.2/30.
  • Remote Subnet: Specify the subnet of your on-premises data center. In this example, set it to 10.1.123.0/24 for virtual interface VIF-A and 192.168.3.0/24 for VIF-B.
  • Routing Mode: In this example, BGP is selected.
  • BGP ASN: ASN of the on-premises data center, which must be different from that used on the cloud (such as ASN of the global DC gateways and the enterprise router). In this example, the ASN of virtual interface VIF-A is 64855 and that of VIF-B is 64856.

Attach global DC gateways to the enterprise router.

  • Resource Type: In this example, Peer link is selected.
  • Peer Link Name: Enter a name as required. In this example, the link name of DGW-A is er-attach-dgw-A, and that of DGW-B is er-attach-dgw-B.
  • Peer Link Type: In this example, Enterprise Router is selected.
  • Link To: Select the enterprise router that the global DC gateways to be attached to. In this example, select ER-A for global DC gateways DGW-A and DGW-B.