Under TCP protocol, CLB uses SYN packets for check. While under UDP protocol, CLB uses
ping command for check.
When a real server port is marked as "unhealthy" on the page, troubleshoot via the following procedures:
netstatcommand to check whether there is a process listening on the real server port. If no such process is found, restart the service.
For layer-7 (HTTP protocol) services, when a listener has an exception during health check, troubleshoot via the following steps:
Suppose that both CLB’s frontend port and CVM’s backend port are 80, and the CVM’s private IP is
For a server on Windows, use the following command:
netstat -ano | findstr :80
For a server on Linux, use the following command:
netstat -anp | grep :80
If you can see the listening on
0.0.0.0:80, the configuration is normal.
For Layer-4 CLB, it is considered normal as long as backend port
telnet responds. You can use
telnet 18.104.22.168 80 for testing. For Layer-7 CLB, it is considered normal if an HTTP status code such as 200 is returned. Check as follows:
On Windows, you can directly enter the private IP in the browser of a CVM to test whether it is normal. This example uses
On Linux, you can run the
curl-I command to check whether the status is
HTTP/1.1 200 OK. This example uses the
curl -I 22.214.171.124 command.
Check whether the private network firewall of the server allows port 80 to pass. You can temporarily disable the firewall for the test.
For Windows, run the
firewall.cpl' command to disable the firewall.
For Linux, run the/etc/init.d/iptables stop` command to disable the firewall.