Redirect

I'm not sure I fully comprehend your requirements. But how about this -

 

 

Apply a second monitor to the production pool which hits the maintenance pool members (using the Alias Address/Alias Service Port options if necessary), and leaving the Availability Requirement set to All. When the maintenance monitor goes down (by "changing the header"), that will trigger the LB_FAILED event on the production VIP. Then you can catch it with an iRule:

 

 

when LB_FAILED {

 

HTTP::redirect "http://(maintenance URL)"

 

}