special web page redirection

While you can't check external websites or URLs, you can absolutely make use of the monitor status of the pools on your BIG-IP. So, assuming that abc.com, abc1.com and abc2.com are in a pool (either the same pool or individual pools), you could check to see if those nodes are marked up by your monitors, and direct traffic accordingly.

You'll want to make use of the LB::status and/or the active_members command(s) to perform these checks.

A simple example would be something like:

when HTTP_REQUEST {
  if { [active_members abcPool] > 0 } {
    pool abcPool
  } else {
    HTTP::redirect "http://www.test.com"
  }
}

Let us know if you've got any questions.

Colin