# Modifying ECS Security Group Rules

1. On the ECS details page, click the Security Groups tab and view security group rules. To enable DAS to access the self-built DB instances on ECSs, you need to add an inbound rule with the port set to 3306 (example) and source to 100.0.0.0/8.

   Figure 1 Security group rules
2. Click Manage Rule on the left. On the Inbound Rules tab page, click Add Inbound Rule.

   Figure 2 Adding an inbound rule

   Recommended configuration: Select TCP for Protocol & Port, enter the port number of the self-built database, and set the source to 100.0.0.0/8 or 0.0.0.0/0.

3. On the Outbound Rules tab page, click Add Outbound Rule.

   Figure 3 Adding an outbound rule

   Recommended configuration: Select TCP for Protocol & Port, enter the port number of the self-built database, and set the source to 100.0.0.0/8 or 0.0.0.0/0.

Parent topic: Reference