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A compound type representing an origin server. These can be defined via the API, CLI, web interface, or using the backend declaration in VCL.

backend b1 {
  .host = "192.0.2.1";
  .port = "80";
}

Backends defined via the API, CLI, or web interface will generate a VCL backend definition prefixed with F_. Backends defined in VCL are not prefixed.

The backend used for a request can be changed by setting the value of req.backend, which is typically done in vcl_recv.