Connect VPCs in different regions - Cloud Enterprise Network

You can use Cloud Enterprise Network (CEN) to establish a private network connection between VPCs in different regions.

Prerequisites

Non-overlapping CIDR blocks: Ensure that the CIDR blocks of the VPCs do not overlap.
Zone availability: To ensure zone-level disaster recovery, create vSwitches in at least two different zones in regions where Enterprise Edition transit routers support multiple zones.
Security group rules: Ensure that the security groups associated with your ECS instances allow the necessary traffic. For example, to ping test the connectivity, you must add an inbound rule allowing ICMP traffic.

Sample

Suppose you have two VPCs in separate regions. You can create a CEN, attach the two VPCs to the transit routers in their respective regions, and establish an inter-region connection between the transit routers to let the VPCs communicate.

VPC1	VPC2
Region: Singapore IPv4 CIDR Block: 10.0.0.0/16 vSwitch 1 (Zone A) : 10.0.0.0/24 vSwitch 2 (Zone B) : 10.0.1.0/24 ECS1 IP address: 10.0.0.1	Region: UK (London) IPv4 CIDR Block: 172.16.0.0/16 vSwitch 1 (Zone A) : 172.16.0.0/24 vSwitch 2 (Zone B) : 172.16.1.0/24 ECS2 IP address: 172.16.0.1

Procedure

Step 1: Create a CEN instance

Log on to the CEN console.
On the Instances page, click Create CEN Instance.
In the Create CEN Instance dialog box, enter a Name (for example, cen-inter-region) and then click OK.
When prompted The CEN instance is created, click View Details to enter the details page.

Step 2: Create transit routers

On the instance details page, click Create Transit Router.
In the Create Transit Router dialog box, set Region to Singapore, keep the other parameters as default, and then click OK.
Repeat the process to create another transit router in UK (London).
Verify that both transit routers appear in the list on the instance details page.

Step 3: Create an inter-region connection

In the Singapore transit router's Actions column, click Create Connection > Inter-region.

On the Create Inter-Region Connection page:
- Attachment Name: inter-region-attachment.
- Peer Region: Select UK (London).
- Bandwidth Allocation Mode: Select Pay-By-Data-Transfer. The fees are settled by Cloud Data Transfer (CDT).
Keep the other parameters as default, and click OK.
When the status changes to Ready, click Return to the List.

Step 4: Attach VPCs to transit routers

In the Singapore transit router's Actions column, click Create Connection > Intra-Region.
On the Create Intra-Region Connection page: Instance Type: Select Virtual Private Cloud (VPC). Region: Select Singapore. Attachment Name: `attach1`. Network Instance: Select `VPC1`.To achieve cross-zone disaster recovery, the system automatically selects the two zones where vSwitches have been deployed. If your VPC has only one vSwitch, you need to create at least one more vSwitch in a different zone. Keep the other parameters as default and click OK.
When the status changes to Ready, it indicates that VPC1 has been attached to the transit router. Click Create More Connections and repeat the steps for UK (London) to attach `VPC2`.
When the status changes to Ready, click Return to the List. Click the Instance ID/Name of each transit router, and verify that both VPC connections (named `attach1` and `attach2`) are listed under the respective transit routers.

Step 5: Verify connectivity

Before proceeding, ensure that the security group rules of both ECS instances permit ICMP protocol access.

Log on to ECS1 and run ping 172.16.0.1 to access ECS2:

Route description

In this example, CEN automatically completes associated forwarding and route learning to achieve VPC communication by creating VPC connections and selecting advanced features:

VPC route table: CEN automatically adds routes for 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 to the system route tables of VPC1 and VPC2. Their next hops are the transit router attachments.
Transit router route table: Transit routers automatically learn routes from the attached VPCs and propagate them across the inter-region connection.

TR (Singapore)

Destination CIDR Block	Next Hop	Route Type
10.0.0.0/24	`attach1`	Propagated Routes
10.0.1.0/24	`attach1`	Propagated Routes
172.16.0.0/24	`inter-region-attachment`	Propagated Routes
172.16.1.0/24	`inter-region-attachment`	Propagated Routes

TR (UK London)

Destination CIDR Block	Next Hop	Route Type
10.0.0.0/24	`inter-region-attachment`	Propagated Routes
10.0.1.0/24	`inter-region-attachment`	Propagated Routes
172.16.0.0/24	`attach2`	Propagated Routes
172.16.1.0/24	`attach2`	Propagated Routes

VPC1

Destination CIDR Block	Next Hop	Route Type
10.0.0.0/24	Local	System
10.0.1.0/24	Local	System
10.0.0.0/8	`attach1`	Custom
172.16.0.0/12	`attach1`	Custom
192.168.0.0/16	`attach1`	Custom

VPC2

Destination CIDR Block	Next Hop	Route Type
172.16.0.0/24	Local	System
172.16.1.0/24	Local	System
10.0.0.0/8	`attach2`	Custom
172.16.0.0/12	`attach2`	Custom
192.168.0.0/16	`attach2`	Custom

Important

If the CIDR blocks that you plan do not belong to the three private CIDR blocks, 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16, you need to manually add routes for other VPCs in each VPC's route table.

For example, if the CIDR block of VPC1 is 11.0.X.X/8 and that of VPC2 is 22.0.X.X/8, you must add the following custom route entries in the route tables of VPC1 and VPC2:

Route Table	Destination CIDR Block	Next Hop	Route Type
VPC1	22.0.X.X/8	attach1	Custom
VPC2	11.0.X.X/8	attach2	Custom

Related steps

Connect VPCs across multiple regions: To connect VPCs in more than two regions, create a transit router in each region, establish inter-region connections, and attach the VPCs. Ensure that the CIDR blocks of the VPCs do not overlap.
Quality of Service (QoS): Use traffic scheduling to manage inter-region traffic by classifying traffic and allocating bandwidth resources. This enhances network quality and optimizes resource usage.
Traffic analysis: Transit routers capture traffic information of inter-region connections and generate flow logs. You can analyze inter-region traffic by querying flow logs.

FAQ

How are inter-region connections billed?
You can choose between Pay-By-Data-Transfer and Allocate from Bandwidth Plan. For details, see Billing.
What is the maximum bandwidth for an inter-region connection?
- Pay-By-Data-Transfer: the maximum bandwidth is limited by quota constraints.
- Allocate from Bandwidth Plan: the maximum bandwidth is the value specified in your bandwidth plan.