Configuring a Security Group Rule

Scenarios

A security group is a collection of access control rules for ECSs and RDS DB instances that have the same security protection requirements and are mutually trusted in a VPC.

This section describes how to create a security group to enable specific IP addresses and ports to access RDS.

• When you attempt to connect to an RDS DB instance through an EIP, you need to configure an inbound rule for the security group associated with the DB instance.
• Check whether the ECS and RDS DB instance are in the same security group.
  • If the ECS and RDS DB instance are in the same security group, they can communicate with each other by default. No security group rule needs to be configured.
  • If the ECS and RDS DB instance are in different security groups, you need to configure security group rules for them, separately.
    • RDS DB instance: Configure an inbound rule for the security group with which the RDS DB instance is associated.
    • ECS: The default security group rule allows all outgoing data packets. In this case, you do not need to configure a security rule for the ECS. If not all outbound traffic is allowed in the security group, you need to configure an outbound rule for the ECS.

Precautions

The default security group rule allows all outgoing data packets. ECSs and RDS DB instances can access each other if they are deployed in the same security group. After a security group is created, you can configure security group rules to control access from and to the DB instances in the security group.

• By default, you can create a maximum of 500 security group rules.
• Too many security group rules will increase the first packet latency. You are advised to create a maximum of 50 rules for each security group.
• To access an RDS DB instance from resources outside the security group, you need to configure an inbound rule for the security group associated with the RDS DB instance.

If you use 0.0.0.0/0, you enable all IP addresses to access RDS DB instances in the security group.

Procedure

1. Log in to the management console.
2. Under Network, click Virtual Private Cloud.
3. In the navigation pane on the left, choose Access Control > Security Groups.
4. On the Security Groups page, locate the target security group and click Manage Rule in the Operation column.
5. On the displayed page, click Add Rule.
6. In the displayed dialog box, set required parameters to add an inbound rule.
7. Click OK.