send redirect if no pool memebers available

Unfortunately v4.x iRules do not allow to check number of available members in a pool. However, you may be able to achieve you goal by defining a fallback URL in your pool which makes the BIG-IP issue a redirect if all no pool members are available. The redirect will have to point to a virtual that sends where you need to go if no there are no members available in the "flashline.kent.edu_636" pool. So, the entire process will require 2 redirect in case of no available pool members. One form the front-end virtual to the portal and possibly a second one from the portal to another version of the frontend (this time without the redirect) if no portal servers are available.