VPN Gateway:Connect a VPC to a data center by using an IPsec-VPN connection in single-tunnel mode and enable BGP dynamic routing

Prerequisites

• A public IP address is assigned to the gateway device in the data center before you associate an IPsec-VPN connection with a public VPN gateway.

• The gateway device in the data center must support the IKEv1 or IKEv2 protocol to establish an IPsec-VPN connection with a transit router.

• The CIDR block of the data center does not overlap with the CIDR block of the network to be accessed.

Regions that support BGP dynamic routing

Scenario

The following figure shows the scenario that is used in this topic. An enterprise has created a VPC in the Germany (Frankfurt) region. The private CIDR block of the VPC is 10.0.0.0/8 and the autonomous system number (ASN) is 65530. The enterprise has a data center in Frankfurt. The public IP address of the data center is 2.XX.XX.2, the private CIDR block is 172.17.0.0/16, and the ASN is 65531. The enterprise wants to establish a connection between the VPC and the data center for business development.

Preparations

• A VPC is created in the Germany (Frankfurt) region and cloud services are deployed in the VPC. For more information, see Create a VPC with an IPv4 CIDR block.

• Before you use VPN Gateway, you must read and understand the security group rules that apply to the ECS instances in VPCs. Make sure that the security group rules allow gateway devices in the data center to access cloud resources. For more information, see View security group rules and Add a security group rule.

Procedure

Step 1: Create a VPN gateway

1. Log on to the VPN gateway console.

2. On the VPN Gateways page, click Create VPN Gateway.

3. On the buy page, configure the parameters that are described in the following table, click Buy Now, and then complete the payment.

   The following table describes only the parameters that are relevant to this topic. You can use the default values of other parameters or leave them empty. For more information, see Create and manage a VPN gateway.

   Parameter	Description
   Region and Zone	The region in which you want to create the VPN gateway. Make sure that the VPN gateway and the VPC reside in the same region. In this example, Germany (Frankfurt) is selected.
   Gateway Type	The gateway type. Default value: Standard.
   Network Type	The network type. In this example, Public is selected.
   Tunnels	The system displays the tunnel modes that are supported in this region. Valid values: Single-tunnel Dual-tunnel For more information, see [Upgrade notice] IPsec-VPN connections support the dual-tunnel mode.
   VPC	The VPC in which you want to create the VPN gateway. In this example, the VPC that is created in the Germany (Frankfurt) region is selected.
   VSwitch	Select a vSwitch from the selected VPC. If you select Single-tunnel, you need to specify only one vSwitch. If you select Dual-tunnel, you need to specify two vSwitches. After the IPsec-VPN feature is enabled, the system creates an elastic network interface (ENI) for each of the two vSwitches as an interface to communicate with the VPC over an IPsec-VPN connection. Each ENI occupies one IP address in the vSwitch. Note The system selects a vSwitch by default. You can change or use the default vSwitch. After a VPN gateway is created, you cannot modify the vSwitch associated with the VPN gateway. You can view the vSwitch associated with the VPN gateway, the zone to which the vSwitch belongs, and the ENI in the vSwitch on the details page of the VPN gateway.
   vSwitch 2	Ignore this parameter if you select Single-tunnel for the Tunnels parameter.
   IPsec-VPN	Specifies whether to enable IPsec-VPN. In this example, Enable is selected.
   SSL-VPN	Specifies whether to enable SSL-VPN. In this example, Disable is selected.

Step 2: Enable BGP dynamic routing

BGP is used to exchange routing information between different ASs. To use the BGP dynamic routing feature, you must enable the BGP dynamic routing feature for the VPN gateway.

1. In the left-side navigation pane, choose Interconnections > VPN > VPN Gateways.

2. In the top navigation bar, select the region in which the VPN gateway resides.

3. On the VPN Gateways page, find the created VPN Gateway and turn on the switch in the Enable Automatic Route Advertisement column.

   After the BGP dynamic routing feature is enabled, the VPN Gateway automatically advertises BGP routes to the VPC.

Step 3: Create a customer gateway

You can create a customer gateway to register the public IP address and BGP AS of the data center to Alibaba Cloud.

1. In the left-side navigation pane, choose Interconnections > VPN > Customer Gateways.

2. In the top navigation bar, select the region in which you want to create the customer gateway.

   Note

   The customer gateway and the VPN gateway to be connected must be deployed in the same region.

3. On the Customer Gateway page, click Create Customer Gateway.

4. In the Create Customer Gateway panel, configure the parameters that are described in the following table and click OK.

   The following table describes only the parameters that are relevant to this topic. You can use the default values of other parameters or leave them empty. For more information, see Create and manage a customer gateway.

   Parameter	Description
   IP Address	The public IP address of the gateway device in the data center. In this example, 2.XX.XX.2 is used.
   ASN	The ASN of the gateway device in the data center. In this example, 65531 is used.

Step 4: Create an IPsec-VPN connection

1. In the left-side navigation pane, choose Interconnections > VPN > IPsec Connections.

2. In the top navigation bar, select the region in which you want to create the IPsec-VPN connection.

   Note

   The IPsec-VPN connections must be created in the same region as the VPN gateway created in Step 1.

3. On the IPsec Connections page, click Create IPsec-VPN Connection.

4. On the Create IPsec-VPN Connection page, configure the parameters that are described in the following table and click OK.

   The following table describes only the parameters that are relevant to this topic. You can use the default values of other parameters or leave them empty. For more information, see Create and manage IPsec-VPN connections in single-tunnel mode.

   Parameter	Description
   Associate Resource	Select the type of network resource to be associated with the IPsec-VPN connection. In this example, VPN Gateway is selected.
   VPN Gateway	The VPN gateway to be associated with the IPsec-VPN connection. In this example, the VPN gateway that is created in Step 1 is selected.
   Routing Mode	The routing mode. Valid values: Destination Routing Mode or Protected Data Flows. If the IPsec-VPN connection uses BGP dynamic routing, we recommend that you select Destination Routing Mode. In this example, Destination Routing Mode is selected.
   Effective Immediately	Specifies whether to immediately start negotiations for the connection. Valid values: Yes: immediately starts IPsec-VPN negotiations after the IPsec-VPN connection is created. No: starts IPsec-VPN negotiations when inbound traffic is detected. In this example, Yes is selected.
   Customer Gateway	The customer gateway to be associated with the IPsec-VPN connection. In this example, the customer gateway that is created in Step 3 is selected.
   Pre-Shared Key	The pre-shared key that is used for authentication. The pre-shared keys must be the same on both the VPN gateway associated with the IPsec-VPN connection and the gateway device in the data center. In this example, 123456**** is used.
   Enable BGP	Specify whether to enable Border Gateway Protocol (BGP). If you want to use BGP routing for the IPsec-VPN connection, turn on Enable BGP. By default, Enable BGP is turned off. In this example, Enable BGP is turned on.
   Local ASN	The local ASN of the tunnel. Default value: 45104. In this example, 65530 is used.
   Encryption Configuration	Use the default values of parameters except for the following parameters. Set the DH Group parameter in the IKE Configurations section to group14. Set the DH Group parameter in the IPsec Configurations section to group14. Note You must configure parameters in the Encryption Configuration section based on the gateway device in the data center to ensure that the encryption configurations of the IPsec-VPN connection are consistent with those of the gateway device in the data center.
   BGP Configuration	Tunnel CIDR Block The CIDR block of the IPsec tunnel. In this example, 169.254.10.0/30 is used. Local BGP IP address The BGP IP address on the VPC side. The IP address must fall within the CIDR block of the IPsec tunnel. In this example, 169.254.10.1 is used.

5. In the Created message, click OK.

Step 5: Add VPN configurations to the gateway device in the data center

After you create an IPsec-VPN connection, you need to add the VPN configurations to the gateway device in the data center to establish a VPN connection between the VPC and the data center.

1. Download the VPN configurations to be added to the gateway device in the data center. For more information, see the "Download the configurations of an IPsec-VPN connection" section of the Create and manage IPsec-VPN connections in single tunnel mode topic.

2. Add the VPN configurations to the gateway device in the data center. For more information, see the Configure an IPsec-VPN configuration in single-tunnel mode section

   of the Load the IPsec-VPN configuration to a Cisco firewall device topic.

   After the IPsec-VPN connection is created, routes are automatically advertised based on BGP dynamic routing.

   • After you advertise the CIDR block of the data center by using BGP dynamic routing on the gateway device in the data center, the VPN gateway on Alibaba Cloud automatically advertises the routes that are learned from the data center to the system route table of the VPC. You can view route information about the system route table on the Dynamic Route tab.

   • The VPN Gateway on Alibaba Cloud automatically learns the system routes from the system route table of the VPC and automatically advertises the routes to the gateway device in the data center.

Step 6: Test the connectivity

1. Log on to an Elastic Compute Service (ECS) instance in the VPC. For more information about how to log on to an ECS instance, see Connection method overview.

2. Run the ping command to access a client in the data center and check the connectivity.

   The result shows that the ECS instance in the VPC can access the client in the data center.

3. Log on to the client in the data center.

4. Run the ping command to access the ECS instance in the VPC and check the connectivity.

   The result shows that the client in the data center can access the ECS instance in the VPC.