stubborn 4xx/5xx Error Handler

Can you clarify this? If the pool member responds with a 4xx or 5xx status, the first response still gets through to the client but any subsequent response is redirected? Is that what you mean?

Can you add logging to the rule to check this?

when HTTP_REQUEST {
   set myhost [HTTP::host]
}
when HTTP_RESPONSE {
   log local0. "[IP::client_addr]:[TCP::client_port]: Request $myhost generated response status: [HTTP::status]"
   if { ([HTTP::status] starts_with "4")} {
      log local0. "[IP::client_addr]:[TCP::client_port]: Redirecting to 4xx.htm"
      HTTP::redirect https://$myhost/images/errors/err_4xx.htm
   } elseif { ([HTTP::status] starts_with "5")} {
      log local0. "[IP::client_addr]:[TCP::client_port]: Redirecting to 5xx.htm"
      HTTP::redirect https://$myhost/images/errors/err_5xx.htm
   } else {
      log local0. "[IP::client_addr]:[TCP::client_port]: Doing nothing"
   }
}

You can check the log output by tailing the ltm log file (tail -f /var/log/ltm).

Aaron