Rewriting - syntax

For performance reasons I'd suggest an else in there... However you may also want to investigate using a switch statement, or using a class (DataGroup) and the findclass/class commands to lookup the recieved host and return the redirection host (The findclass should scale better, and mean you don't have to re-write your iRule whenever you add a new host).

e.g. (Without checking for syntax, this is for v10)

  
  when HTTP_REQUEST {   
    set redirecthost [class search -value "theclass" equals [HTTP::host]]   
    if { $redirecthost ne "" } {  
      HTTP::redirect $redirecthost  
    }  
  }  
  

You can add the embelishments...