hosting maintenance page via ifile utilizing an irule

Hope Below iRule helps. Change the Pool_Name to your server pool name.

when CLIENT_ACCEPTED {
  if { [active_members Pool_Name ] >= 1 } {
   pool Pool_Name
  } 
  else {
    HTTP::respond 200 content {   Sorry Page   Sorry, The website is not available. Please try again later  }
    }
}

-Jinshu