Error 502 occurs after a high defense IP address is configured for the server
September 04,2021
Server users in order to ensure the stability of the business operation and avoid the destruction of the cyber attacks, so choose good prevention services to the server configuration, but there are some server users access services access high website later suggests a 502 error, below small make up is to analyze the server configuration is high after the IP website in 502 a common cause of errors and solutions.

Cause one: The high anti-loopback source IP address is blocked or limited by the source station

After the server is configured with a high defense IP address, the source IP address is hidden because a high defense IP address is in the middle proxy. Therefore, from the point of view of the source site, all client IP addresses that pass through the high-defense IP address will become the high-defense source IP address. In normal cases, a client requests to access a high defense IP address. After receiving the request, the high defense IP address converts the source IP address of the real client into a high defense source IP address and sends the request to the American server. However, if the source IP address is exposed, the client can directly request access to the source, bypassing the protection provided by a high IP address.

If the high IP proxy service is not configured, the real client addresses are scattered on the source site. Generally, the number of requests from each client IP address is small. However, after the high IP proxy service is configured, the source IP address segment is fixed and limited. Therefore, the source site considers that all access requests come from the high loopback source IP address segment, and the request volume allocated to each source IP address increases. As a result, the server mistakenly believes that the high loopback source IP address attacks the source site. In this case, if the server has a security policy to defend against DDoS attacks, it is likely to block the source IP address or limit the rate.

According to the principle, error 502 can be resolved by allowing all the high anti-loopback source IP addresses on the server. There are two methods for setting the source IP address:

1) View the high loopback source IP address segment to obtain the high loopback source IP address, and add the high loopback source IP address segment to the whitelist in the server firewall and host security protection software.

2) Disable the firewall and host security protection software on the server.

Cause two: The source site is abnormal. As a result, the response request times out

The exceptions of the server source site include:

1. The source IP is exposed and the attack leads to paralysis;

2. Physical failure of the source server room;

3. Web programs such as Apache and Nginx in the source server are faulty;

4. The server memory and CPU usage are too high, resulting in poor performance.

5. The uplink of the source site is congested and blocked.

You can modify the hosts file on the local host to direct the domain name to the source IP address. If you directly access the host through the source IP address, you cannot access the host because of packet loss caused by Ping value or Telnet timeout.

Refer to the following steps to rectify the fault:

1. Check whether the traffic and request volume of the source site increase greatly, and compare the monitoring on the high IP management console. If the server is attacked by heavy traffic but no exception is displayed on the high IP management console, the attack may bypass the high IP address and directly attack the server. In this case, you are advised to change the source IP address as soon as possible.

2. After troubleshooting the attack cause, you can view the server process status, CPU and memory usage, and bandwidth monitoring. If any exception occurs, contact technical support personnel for troubleshooting.

3. If error 502 occurs on a few clients, you are advised to collect the IP address of the client and the time when the exception occurs, and report the error to the after-sale technology of the server for troubleshooting.

The above is about the server configuration of high defense IP site 502 error analysis and solutions, I hope to help the need for server users.