ApsaraDB for Redis:What do I do if I cannot connect an ECS instance to an ApsaraDB for Redis instance?

Step 1: Check whether the error message is invalid password, WRONGPASS, or NOAUTH Authentication required

If the error message is connection timed out or no explicit error message is displayed, skip Step 1 and proceed to Step 2.

Error description

If the error message is invalid password, WRONGPASS invalid username-password pair, or NOAUTH Authentication required, the account and password are incorrect.

Solution

• Use a password in the <user>:<password> format to re-establish the connection. For example, if the username of the custom account is testaccount and the password is Rp829dlwa, enter testaccount:Rp829dlwa as the password.

• If a password error is still reported when you use a password in the <user>:<password> format to reconnect the ECS instance to the ApsaraDB for Redis instance, you may have entered the wrong password. In this case, reset the password and use the new password to establish the connection. For more information about how to reset the password, see Change or reset the password.

Step 2: Run the ping command to check whether the ECS instance is connected to the ApsaraDB for Redis instance

Procedure

Log on to the ECS instance and run the ping command.

ping <host>

Example: ping r-bp1zx****.redis.rds.aliyuncs.com

Result description

If the ping operation is successful, the network is connected, as shown in the following result illustrations. You can proceed to Step 3 for further troubleshooting.

If the ping operation fails, the network is not connected.

Common causes and solutions

• The ECS instance and the ApsaraDB for Redis instance may belong to different VPCs.

  Check whether the ECS instance and the ApsaraDB for Redis instance belong to the same VPC. For more information, see How do I check whether an ECS instance and an ApsaraDB for Redis instance are of the same network type?

  If the ECS instance and the ApsaraDB for Redis instance belong to different VPCs, you can perform the following operations:

  • Change the VPC of the ECS instance. For more information, see Change the VPC of an ECS instance.

  • Connect the ECS instance to the ApsaraDB for Redis instance over the Internet. For information about how to apply for a public endpoint, see Apply for a public endpoint for an ApsaraDB for Redis instance.

    Important

    Compared with the Internet, VPCs provide better security and performance. Therefore, we recommend that you use a VPC to connect to the ApsaraDB for Redis instance.

• The outbound access rule of the security group of the ECS instance may block traffic to the vSwitch or VPC IP address of the ApsaraDB for Redis instance.

  Check whether the ECS security group has an outbound rule whose protocol type is ICMP (IPv4) and whether the rule blocks traffic to the vSwitch or VPC IP address of the ApsaraDB for Redis instance.

  If yes, allow access to the vSwitch or VPC IP address of the ApsaraDB for Redis instance. For more information, see Add a security group rule.

  Note

  To view the vSwitch or VPC IP address, click the ID of the VSwitch or VPC on the Instance Information page in the ApsaraDB for Redis console. On the page that appears, view the IPv4 CIDR block.

If the connection still fails, see Run the PING command to check the connection between an ECS instance and an ApsaraDB for Redis instance.

Step 3: Run the telnet command to check whether the service port is available

Procedure

Log on to the ECS instance and run the telnet command.

telnet <host> <port>

Example: telnet r-bp1zx****.redis.rds.aliyuncs.com 6379

Result description

If Connected to ... is returned or the telnet interface is displayed, as shown in the following result illustrations, the port is available.

If the "Connection timed out" or "Connect failed" message is displayed, the connection fails.

Common causes and solutions

• The whitelist is incorrectly configured or no whitelist is configured. For more information, see Step 4: Check the whitelist.

• The outbound access rule of the security group of the ECS instance may block traffic on the service port of ApsaraDB for Redis.

  Check whether the ECS security group has an outbound rule whose protocol type is TCP and whether the rule blocks traffic to the service port of ApsaraDB for Redis. The default port is 6379. If yes, allow access to the ApsaraDB for Redis instance over the port. For more information, see Add a security group rule.

If the connection still fails, see Use the telnet command to check the connection to the service port of ApsaraDB for Redis.

Step 4: Check the whitelist

The common cause of connection failure is that the whitelist is incorrectly configured or no whitelist is configured. In the following two scenarios, we recommend that you check the whitelist.

• The domain name can be pinged, but the telnet operation fails.

• If you use redis-cli to connect to the VPC endpoint of the ApsaraDB for Redis instance from the ECS instance, the (error) ERR illegal address or (error) ERR client ip is not in whitelist error is reported.

Common causes

• An incorrect IP address is configured.

  For example, you connect the ECS instance to the VPC endpoint of the ApsaraDB for Redis instance, but mistakenly add the public IP address of the ECS instance to the whitelist of the ApsaraDB for Redis instance. Alternatively, you connect the ECS instance to the public endpoint of the ApsaraDB for Redis instance, but mistakenly add the primary private IP address of the ECS instance to the whitelist of the ApsaraDB for Redis instance.

• No whitelist is configured.

Solution 1

You can check whether the IP address of the ECS instance has been added to the whitelist of the ApsaraDB for Redis instance by performing connection diagnostics. You can also add the IP address of the ECS instance to the whitelist. For more information, see Perform diagnostics on connections.

Solution 2

1. Check whether the endpoint that you use is a VPC endpoint or a public endpoint. For more information, see View endpoints.

2. If the endpoint is a VPC endpoint, add the primary private IP address of the ECS instance to the whitelist of the ApsaraDB for Redis instance. If the endpoint is a public endpoint, add the public IP address of the ECS instance to the whitelist of the ApsaraDB for Redis instance. For more information, see Configure whitelists.

   Note

   For information about how to query the IP address of an ECS instance, see Network FAQ.

References

• For information about the reasons why an on-premises device fails to connect to an ECS instance and the troubleshooting method, see How do I troubleshoot connection issues in ApsaraDB for Redis?

• For information about how to connect an ECS instance to an ApsaraDB for Redis instance across Alibaba Cloud accounts, see How do I connect an ECS instance to an ApsaraDB for Redis instance across accounts?