how to rewrite fallback page

 
 when HTTP_REQUEST { 
  
     Set the fallback host based on the requested host. 
    HTTP::fallback "http://[HTTP::host]/notices/maintenance.html" 
 } 
 

 
   when RULE_INIT {   
  
       Use a prefix for the path that does not already exist in the application 
      set ::maintenance_prefix "/maintenance/" 
  
       The default maintenance page 
      set ::maintenance_page "maintenance.html" 
   }   
   when CLIENT_ACCEPTED {   
  
       Save the name of the default pool on the VIP 
      set default_pool [LB::server pool] 
   }   
   when HTTP_REQUEST {   
  
       Check if there aren't any active members in the default pool 
      if { [active_members $default_pool] < 1 } {  
  
          Primary members are unavailable.  Check if the URI has not already been rewritten. 
         if {not ([HTTP::path] starts_with $::maintenance_prefix)}{   
  
             Rewrite the URI to the maintenance prefix/maintenance page (/maintenance/maintenance.html)   
            HTTP::uri "$::maintenance_prefix$::maintenance_page" 
         }   
          Use the maintenance pool 
         pool maintenance_pool  
  
      } else {  
  
          Use the VIP's default pool 
         pool $default_pool  
      }  
   }