Help Center/ Elastic Load Balance/ FAQs/ Service Abnormality/ How Do I Handle Abnormal Request Headers?
Updated on 2025-08-30 GMT+08:00
View PDF

How Do I Handle Abnormal Request Headers?

In addition to abnormal status codes, ELB notifies clients of typical exceptions through the x-router-code header. Common header values are 40000, 40001, 50000, and 50001. You can handle these headers based on the following table.

Table 1 Abnormal headers

Header Value

Meaning

Possible Causes

40000

The default backend server group has no backend servers.
  • The client request does not match any forwarding policy.
  • No backend server is configured for the backend server groups.

40001

The backend server group of the matched forwarding policy has no backend servers.
  • An unexpected forwarding policy is matched by accident.
  • The backend server group of the matched forwarding policy has no backend servers.

50000

All backend servers are unavailable.
  • The health check is not correctly configured. As a result, ELB considers that all backend servers are unhealthy.
  • All backend servers themselves are unavailable.

50001

The configuration is loading.

The configuration is not complete. Wait and try again later.
Parent topic: Service Abnormality