Note: In this example, All the ports and IP address are demonstration environment parameter values. You must configure the ports and internal IP address based on your business requirements.
| No. | Possible cause | Solution |
|---|---|---|
| 1 | ELB does not support FTP, TFTP, H.323, and SIP protocols. | 1. For a Linux system, you can configure the forwarding of port 22 and use SFTP to connect and transmit data. 2. You can associate an elastic IP address (EIP) with an FTP server in cut-through mode to provide external FTP service. |
| 2 | The internal firewall of the server does not allow traffic on port 80. | You can run the following commands to temporarily disable the firewall to perform a test. 1. For a Windows server, run the following command: firewall.cpl 2. For a Linux server, run the following command: /etc/init.d/iptables stop |
| 3 | A backend port exception occurs. | • For Layer 4 ELB, you can perform a Telnet test. If you receive a response, the backend port functions properly.For example, you can run the following command to perform a test: telnet 10.11.192.1 80.• For Layer 7 ELB, you can check the returned HTTP status code. The status code must be a status code that indicates a normal condition, such as 200. You can use the following methods to test whether the backend port is normal: • Windows: Access the internal IP address of the ECC instance to check the connectivity. Example: <http://10.11.192.1> • Linux: Run the curl -I command to check whether the status is HTTP/1.1 200 OK.Example: curl -I 10.11.192.1 |
| 6 | The rp_filter feature conflicts with the policy-based routing mechanism of the Linux Virtual Server (LVS) for ELB. | 1. Log on to the ECC instance that is attached to Layer 4 ELB. The ECC instance runs a Linux system. 2. Edit the /etc/sysctl.conf file and set the following parameters in the system configuration file to 0: net.ipv4.conf.default.rp_filter = 0 net.ipv4.conf.all.rp_filter = 0 net.ipv4.conf.eth0.rp_filter = 03. Run the sysctl -p command to make the configurations take effect. |
| 7 | A listener exception occurs. | Run the following commands on the server. If you can see the listening information of 10.11.192.1:80 or 0.0.0.0: 80, the listening on the port is normal. • For a Windows server, run the following command: netstat -ano | findstr :80• For a Linux server, run the following command: netstat -anp | grep :80 |
| 8 | An exception occurs on the on-premises network of the client or the intermediate link of the service provider. | Test the connectivity on the service port of the ELB instance in different regions and network environments.If the exception occurs only when the ELB instance is accessed from the on-premises network, it can be determined that the problem is caused by a network exception. You can perform ping and MTR tests for further troubleshooting and analysis. |