Manage communication between a data center and a VPC - Access Control| Alibaba Cloud Documentation Center

This topic describes how to use network access control lists (ACLs) to manage communication between a data center and a virtual private cloud (VPC).

Prerequisites

A VPC and a vSwitch are created. For more information, see Create and manage a VPC and Work with vSwitches.
Elastic Compute Service (ECS) instances are created in the vSwitch. For more information, see Create an instance by using the wizard.
The ECS instances are added to a security group that allows the HTTP services on the ECS instances to be accessed over the Internet. For more information, see Security group rules for websites to provide web services.

Background information

A company has created an Internet-facing Server Load Balancer (SLB) instance and ECS instances. Static pages are hosted on the ECS instances. A listener has been configured for the SLB instance, and the ECS instances are added as backend servers for the SLB instance. By default, Data Center 1 and Data Center 2 can access the static pages through the public IP address of the SLB instance. To meet business requirements, the company wants to allow Data Center 1 to access the static pages, and deny access from Data Center 2 to the static pages.

The following table lists the public IP addresses of the data centers and the SLB instance.


Network	Public IP address
Data Center 1	111.XX.XX.111
Data Center 2	222.XX.XX.222
SLB instance	33.XX.XX.33

You can associate a network ACL with the vSwitch to which the ECS instances belong. Then, you can configure network ACL rules to control inbound and outbound network traffic transmitted through the vSwitch.

The following flowchart shows the procedure.

Step 1: Create a network ACL

Log on to the VPC console.
In the left-side navigation pane, choose ACL > Network ACL.
In the top navigation bar, select the region where the network ACL is created.
On the Network ACL page, click Create Network ACL.
In the Create Network ACL dialog box, set the following parameters and click OK:
- VPC: Select the VPC for which you want to create the network ACL.
- Name: Enter a name for the network ACL.
  The name must be 2 to 128 characters in length and can contain digits, underscores (_), and hyphens (-). It must start with a letter.
- Description: Enter a description for the network ACL.
  The description must be 2 to 256 characters in length. It cannot start with http:// or https://.

Step 2: Associate the network ACL with a vSwitch

Log on to the VPC console.
In the left-side navigation pane, choose ACL > Network ACL.
In the top navigation bar, select the region where the network ACL is created.
On the Network ACL page, find the network ACL that you want to manage and click its ID.
On the Resources tab, click Associate vSwitch.
In the Associate vSwitch dialog box, select the vSwitch and click OK.

Step 3: Add rules to the network ACL

Add inbound and outbound rules to the network ACL.

Log on to the VPC console.
In the left-side navigation pane, choose ACL > Network ACL.
In the top navigation bar, select the region where the network ACL is created.
On the Network ACL page, find the network ACL that you want to manage and click Inbound Rule in the Actions column.
On the Inbound Rule tab, click Manage Inbound Rule.

Set the following parameters and click OK.


Priority	Rule Name	Action	Protocol	Source IP Addresses	Destination Port Range
1	Allow-HTTP-requests-from-Data-Center-1	Accept	TCP	The public IP address of Data Center 1. `111.XX.XX.111` is used in this example.	`80/80`
3	Drop-HTTP-requests-from-Data-Center-2	Drop	TCP	The public IP address of Data Center 2. `222.XX.XX.222` is used in this example.	`80/80`

You must add the following inbound rule if the health check feature is enabled for the SLB instance.


Priority	Rule Name	Action	Protocol	Source IP Addresses	Destination Port Range
2	Allow-health-checks	Accept	ALL	The CIDR block used to perform health checks. Set the value to `100.64.0.0/10`.	`-1/-1`

Click the Outbound Rule tab, and then click Manage Outbound Rule.

Set the following parameters and click OK.


Priority	Rule Name	Action	Protocol	Destination IP Address	Destination Port Range
1	Allow-HTTP-traffic-destined-for-Data-Center-1	Accept	TCP	The public IP address of Data Center 1. `111.XX.XX.111` is used in this example.	`80/80`
3	Drop-HTTP-requests-destined-for Data-Center-2	Drop	TCP	The public IP address of Data Center 2. `222.XX.XX.222` is used in this example.	`80/80`

You must add the following outbound rule if you enable the health check feature for the SLB instance.


Priority	Rule Name	Action	Protocol	Destination IP Address	Destination Port Range
2	Allow-health-checks	Accept	ALL	The CIDR block used to perform health checks. Set the value to `100.64.0.0/10`.	`-1/-1`

Step 4: Test the connectivity

To test the connectivity between the data centers and the SLB instance, perform the following steps:

Open the browser on a computer in Data Center 1.
Enter http://33.XX.XX.33 in the address bar of the browser to test the connectivity.
The result shows that the device in Data Center 1 can access the static pages on the ECS instances.
Open the browser on a device in Data Center 2.
Enter http://33.XX.XX.33 in the address bar of the browser to test the connectivity.
The result shows that the device in Data Center 2 cannot access the static pages on the ECS instances.