Help Center/ Virtual Private Cloud/ User Guide/ VPC Peering Connection/ Creating a VPC Peering Connection to Connect Two VPCs in the Same Account

Updated on 2024-10-25 GMT+08:00

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Creating a VPC Peering Connection to Connect Two VPCs in the Same Account

Scenarios

Two VPCs from the same region cannot communicate with each other by default, but you can use a VPC peering connection to connect them.

The following describes how to create a VPC peering connection to connect two VPCs (vpc-A and vpc-B in this example) in the same account. In this way, instances (ECS-A01 and RDS-B01 in this example) in the two VPCs can communicate with each other.

The procedure is as follows:

Step 1: Create a VPC Peering Connection

Step 2: Add Routes for the VPC Peering Connection

Step 3: Configure Security Group Rules for Instances in Local and Peer VPCs

Step 4: Verify Network Connectivity

Figure 1 Connecting two VPCs in an account using a VPC peering connection

Currently, VPC peering connections are free.

Notes and Constraints

Only one VPC peering connection can be created between two VPCs at the same time.
A VPC peering connection can only connect VPCs in the same region.
- A VPC peering connection can enable a VPC created on the Huawei Cloud Chinese Mainland website to connect to one created on the Huawei Cloud International website, but the VPCs must be in the same region. For example, if the VPC created on the Chinese Mainland website is in the CN-Hong Kong region, then the VPC created on the International website must also be in the CN-Hong Kong region.
- If you want to connect VPCs in different regions, you can use Cloud Connect.
- If you only need a few ECSs in different regions to communicate with each other, you can assign and bind EIPs to the ECSs.
If the local and peer VPCs have overlapping CIDR blocks, the VPC peering connection may not be usable.
In this case, you can configure the network by referring to VPC Peering Connection Usage Examples.

Prerequisites

You have two VPCs from the same account in the same region. If you want to create one, see Creating a VPC and Subnet.

Step 1: Create a VPC Peering Connection

Go to the VPC peering connection list page.
In the upper right corner of the page, click Create VPC Peering Connection.
The Create VPC Peering Connection page is displayed.

Configure the parameters as prompted.

For details, see Table 1.

Figure 2 Creating a VPC peering connection

**Table 1** Parameters for creating a VPC peering connection
Parameter	Description	Example Value
Region	Mandatory The region where the VPC peering connection is created. Select the region nearest to you to ensure the lowest latency possible.	CN-Hong Kong
VPC Peering Connection Name	Mandatory Enter a name for the VPC peering connection. The name can contain a maximum of 64 characters, including letters, digits, hyphens (-), and underscores (_).	peering-AB
Description (Optional)	Optional Enter a description of the VPC peering connection in the text box as required.	peering-AB connects vpc-A and vpc-B.
Local VPC	Mandatory VPC at one end of the VPC peering connection. You can select one from the drop-down list.	vpc-A
Local VPC CIDR Block	CIDR block of the selected local VPC	172.16.0.0/16
Account	Mandatory Options: My account and Another account Select My account.	My account
Peer Project	The project is selected in by default if Account is set to My account. In this example, vpc-A and vpc-B are created in region A, and the corresponding project of the account in region A is selected by default.	ab-cdef-1
Peer VPC	This parameter is mandatory if Account is set to My account. VPC at the other end of the VPC peering connection. You can select one from the drop-down list.	vpc-B
Peer VPC CIDR Block	CIDR block of the selected peer VPC. If the local and peer VPCs have overlapping CIDR blocks, the VPC peering connection may not be usable. For details, see VPC Peering Connection Usage Examples.	172.17.0.0/16

Click Create Now.
A dialog box for adding routes is displayed.
In the displayed dialog box, click Add Now. On the displayed page about the VPC peering connection details, go to Step 2: Add Routes for the VPC Peering Connection to add a route.

Step 2: Add Routes for the VPC Peering Connection

In the lower part of the VPC peering connection details page, click Add Route.
The Add Route dialog box is displayed.

Figure 3 Adding a route

Add routes to the route tables as prompted.

Table 2 describes the parameters.

**Table 2** Parameter description
Parameter	Description	Example Value
VPC	Select a VPC that is connected by the VPC peering connection.	vpc-A
Route Table	Select the route table of the VPC. The route will be added to this route table. Each VPC comes with a default route table to control the outbound traffic from the subnets in the VPC. In addition to the default route table, you can also create a custom route table and associate it with the subnets in the VPC. Then, the custom route table controls outbound traffic of the subnets. If there is only the default route table in the drop-down list, select the default route table. If there are both default and custom route tables in drop-down list, select the route table associated with the subnet connected by the VPC peering connection.	rtb-vpc-A (Default)
Destination	An IP address or address range in the VPC being connected by the VPC peering connection. The value can be a VPC CIDR block, subnet CIDR block, or ECS IP address. For details about the route configuration example, see VPC Peering Connection Usage Examples.	vpc-B CIDR block: 172.17.0.0/16
Next Hop	The default value is the current VPC peering connection. You do not need to specify this parameter.	peering-AB
Description	Supplementary information about the route. This parameter is optional. The description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	Route from vpc-A to vpc-B
Add a route for the other VPC	If you select this option, you can also add a route for the other VPC connected by the VPC peering connection. To enable communications between VPCs connected by a VPC peering connection, you need to add both forward and return routes to the route tables of the VPCs. For details, see VPC Peering Connection Usage Examples.	Selected
VPC	By default, the system selects the VPC connected by the VPC peering connection. You do not need to specify this parameter.	vpc-B
Route Table	Select the route table of the VPC. The route will be added to this route table. Each VPC comes with a default route table to control the outbound traffic from the subnets in the VPC. In addition to the default route table, you can also create a custom route table and associate it with the subnets in the VPC. Then, the custom route table controls outbound traffic of the subnets. If there is only the default route table in the drop-down list, select the default route table. If there are both default and custom route tables in drop-down list, select the route table associated with the subnet connected by the VPC peering connection.	rtb-vpc-B (Default)
Destination	An IP address or address range in the other VPC connected by the VPC peering connection. The value can be a VPC CIDR block, subnet CIDR block, or ECS IP address. For details about the route configuration example, see VPC Peering Connection Usage Examples.	vpc-A CIDR block: 172.16.0.0/16
Next Hop	The default value is the current VPC peering connection. You do not need to specify this parameter.	peering-AB
Description	Supplementary information about the route. This parameter is optional. The description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	Route from vpc-B to vpc-A.

Click OK.
You can view the routes in the route list.

Step 3: Configure Security Group Rules for Instances in Local and Peer VPCs

When configuring security group rules to control traffic in and out of ECS-A01 and RDS-B01, you can set Preset Rule to Custom rule. Table 3 shows the preset security group rules.

**Table 3** Preset security group rules (Custom rules)
Direction	Action	Type	Protocol & Port	Source/Destination	Description
Inbound	Allow	IPv4	All	Source: current security group	Allows the instances in the security group to communicate with each other over any IPv4 protocol and port.
Inbound	Allow	IPv6	All	Source: current security group	Allows the instances in the security group to communicate with each other over any IPv6 protocol and port.
Outbound	Allow	IPv4	All	Destination: 0.0.0.0/0	Allows all IPv4 traffic from the instances in the security group to external resources over any protocol and port.
Outbound	Allow	IPv6	All	Destination: ::/0	Allows all IPv6 traffic from the instances in the security group to external resources over any protocol and port.

As you can see, the above preset rules only allow instances in the security group to communicate with each other. To allow external traffic to access the instances in the security group, add inbound rules by referring to Adding a Security Group Rule.

If the instances in the local and peer VPCs are associated with the same security group, they can communicate with each other.
For example, if ECS-A01 and RDS-B01 are associated with security group Sg-AB, you only need to perform the operations in 1 to allow remote logins.
If the instances in the local and peer VPCs are associated with different security groups, they cannot communicate with each other unless you add rules to allow them to.
For example, if ECS-A01 is associated with security group Sg-A, and RDS-B01 is associated with security group Sg-B, you need to perform the operations in 1 and 2 to allow remote logins.

Add security group rules in Table 4 to allow remote logins.

**Table 4** Security group rules for remote logins
Direction	Action	Type	Protocol & Port	Source	Description
Inbound	Allow	IPv4	TCP: 22	IP address: 0.0.0.0/0	Allows any IPv4 address to remotely log in to the Linux instances in Sg-AB over SSH port 22.
Inbound	Allow	IPv4	TCP: 3389	IP address: 0.0.0.0/0	Allows any IPv4 address to remotely log in to the Windows instances in Sg-AB over RDP port 3389.

(Optional) Add security rules to allow the instances in Sg-A and Sg-B to communicate with each other.

Select either of the following solution based on your service requirements.

Solution 1 in Table 5: Set Source to the CIDR block of peer VPC or subnet.

**Table 5** Security group rules (CIDR block as the source)
Security Group	Direction	Action	Type	Protocol & Port	Source	Description
Sg-A	Inbound	Allow	IPv4	All	IP address: 172.17.0.0/16 (vpc-B CIDR block)	Allows traffic from 172.17.0.0/16 to access instances in Sg-A over any IPv4 protocol and port.
Sg-B	Inbound	Allow	IPv4	All	IP address: 172.16.0.0/16 (vpc-A CIDR block)	Allows traffic from 172.16.0.0/16 to access instances in Sg-B over any IPv4 protocol and port.

Solution 2 in Table 6: Set Source to Sg-A and Sg-B.

**Table 6** Security group rules (security group as the source)
Security Group	Direction	Action	Type	Protocol & Port	Source	Description
Sg-A	Inbound	Allow	IPv4	All	Sg-B	Allows instances in Sg-B to access those in Sg-A over any IPv4 protocol and port.
Sg-B	Inbound	Allow	IPv4	All	Sg-A	Allows instances in Sg-A to access those in Sg-B over any IPv4 protocol and port.

Step 4: Verify Network Connectivity

After you add routes for the VPC peering connection, verify communications between the local and peer VPCs.

Log in to ECS-A01 in the local VPC.
Multiple methods are available for logging in to an ECS. For details, see Logging In to an ECS.
Check whether ECS-A01 can communicate with RDS-B01.
ping RDS-B01-IP-address

Example command:

ping 172.17.0.21
If information similar to the following is displayed, ECS-A01 and RDS-B01 can communicate with each other, and the VPC peering connection between VPC-A and VPC-B is successfully created.
```
[root@ecs-A01 ~]# ping 172.17.0.21
PING 172.17.0.21 (172.17.0.21) 56(84) bytes of data.
64 bytes from 172.17.0.21: icmp_seq=1 ttl=64 time=0.849 ms
64 bytes from 172.17.0.21: icmp_seq=2 ttl=64 time=0.455 ms
64 bytes from 172.17.0.21: icmp_seq=3 ttl=64 time=0.385 ms
64 bytes from 172.17.0.21: icmp_seq=4 ttl=64 time=0.372 ms
...
--- 172.17.0.21 ping statistics ---
```
If VPCs connected by a VPC peering connection cannot communicate with each other, refer to Why Did Communication Fail Between VPCs That Were Connected by a VPC Peering Connection?