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 = "";
.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.