Total Newbie needs help....

Hello,

This devcentral article is quite old. You have new options now. here is a little example :

when CLIENT_ACCEPTED {
    set default_pool [LB::server pool]
}

 display maintenance page if no pool members are available
when HTTP_REQUEST {
    if { [active_members $default_pool] < 1 } { 
        HTTP::respond 200 content [ifile get "/Common/maintenance.html"] noserver "Content-Type" "text/html" "Cache-Control" "no-cache, must-revalidate" 
    }
} 

 how to offload backend server error messages
when HTTP_RESPONSE { 
 if {([HTTP::status] starts_with "404") } { 
   if { !([class match $method equals "http_method"]) } {
    HTTP::respond 404 content [ifile get "/Common/404.html"] noserver "Content-Type" "text/html" "Cache-Control" "no-cache, must-revalidate" 
   }
 } 
} 

 display maintenance page when load balancing fail
when LB_FAILED { 
  HTTP::respond 200 content [ifile get "/Common/maintenance.html"] noserver "Content-Type" "text/html" "Cache-Control" "no-cache, must-revalidate" 
}

You just have to upload your maintenance page as an ifile. here the link to ifile description : https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-system-irules-concepts-11-6-0/7.html?sr=53648987