X-Forwarded-Host Configuration help

BIGIP doesn't modify HOST header values by default. So server should receive original HOST header coming from the client. But if you still want to pass it explicitly you can use something sort of below.

when HTTP_REQUEST {
  while {[HTTP::header exists "X-Forwarded-Host"]}{
    HTTP::header remove "X-Forwarded-Host"
  }
  HTTP::header insert "X-Forwarded-Host" [HTTP::host]
}