What Should I Do If an ECS Cannot Connect to an RDS for SQL Server Instance Through a Private Network?

Perform the following steps to identify the problem:

1. Check whether the ECS and RDS for SQL Server instance are located in the same VPC.
   • If they are in the same VPC, go to 2.
   • If they are in different VPCs, create an ECS in the VPC in which the RDS for SQL Server instance is located.

2. Check whether the security group rules of the RDS instance are appropriate.

   For details, see Configuring Security Group Rules.

3. On the ECS, check whether the RDS for SQL Server instance can be connected.

   The default port of RDS for SQL Server is 1433.

   telnet <IP address> {port number}

   • If the DB instance can be connected, the network between the ECS and the DB instance is normal and no further action is required.
   • If the DB instance cannot be connected, contact technical support.